Health calculator glossary: measurements, formulas & concepts

A Body Shape Index (ABSI) is an anthropometric metric that evaluates abdominal fat risk by normalizing waist circumference to height and BMI.

The alveolar-arterial (A-a) oxygen gradient is a clinical measurement of the difference between alveolar and arterial oxygen concentrations, assessing lung gas exchange efficiency.

A1C (Hemoglobin A1c) is a diagnostic blood biomarker measuring the percentage of glycated hemoglobin to estimate average blood glucose levels over the preceding 2 to 3 months.

The absolute eosinophil count (AEC) converts the eosinophil percentage from a WBC differential into an actual cell count, which is what determines eosinophilia severity.

A complete blood count with differential reports lymphocytes as a percentage of the total white blood cell count.

The absolute neutrophil count (ANC) converts a routine CBC differential into a single number that tells you how many infection-fighting neutrophils are actually circulating in the blood.

The absolute reticulocyte count (ARC) converts the reticulocyte percentage from a CBC into an actual cell count, giving a more reliable picture of how hard the bone marrow is working to replace red blood cells.

Acetaminophen (Tylenol) is one of the most commonly given pediatric medications, and also one of the most common causes of accidental drug overdose in children — almost always from stacking too many doses too close together, not from a single large dose.

This calculator compares the added sugar you eat or drink in a day against the American Heart Association's recommended daily limit — 25 g for women and 36 g for men — and converts the total to teaspoons so it's easier to picture.

Premature infants are often compared to developmental milestones designed for full-term babies, which can make a preemie appear "behind" when they are actually right on track for how early they arrived.

Adjusted body weight (AdjBW) is a calculated weight figure used, alongside actual weight and ideal body weight, to estimate medication dosing and nutrition needs for people whose actual weight is well above their ideal weight.

The exercise intensity below which energy production is almost entirely aerobic. Training below this threshold (typically 60–75% of max heart rate) improves base fitness with minimal recovery demand.

A D-dimer test is a common first step when venous thromboembolism (VTE) — deep vein thrombosis or pulmonary embolism — is suspected.

The albumin-to-creatinine ratio (ACR) is a spot urine test that screens for kidney damage by measuring how much albumin leaks into the urine relative to creatinine excretion.

The albumin/globulin (A/G) ratio compares the two main categories of blood protein — albumin and globulin — to help screen for liver disease, kidney disease, and conditions that raise antibody or other globulin levels.

Alcohol is often called an "empty calorie" source because it supplies energy without the nutrients found in most food, and its calories rarely appear on a nutrition label the way a soda's or a snack's do.

Knowing how many alcohol units are in your drink is the single most practical step toward making informed choices about your drinking.

The Aldrete Score is one of the most widely used tools for tracking a patient's recovery from anesthesia and deciding when they are ready to leave the post-anesthesia care unit (PACU).

Maximum allowable blood loss (MABL) estimates how much blood a patient can lose during surgery before their hematocrit falls to a clinician-chosen floor.

Acute appendicitis is one of the most common surgical emergencies, but its presentation overlaps with many other causes of abdominal pain.

The amniotic fluid index (AFI) is one of the two standard ultrasound methods for estimating how much amniotic fluid surrounds the fetus, alongside the single deepest pocket (SDP/DVP) technique.

Amoxicillin dosing for children is not one number — it depends on which infection is being treated, the child's age and weight, and whether the regimen comes from the FDA label or a professional-society guideline.

The exercise intensity at which lactic acid accumulates faster than it can be cleared, causing fatigue. Also called the lactate threshold. Training near this point improves performance and VO2 max.

The anion gap is a quick screening calculation from a basic metabolic panel — sodium minus the sum of chloride and bicarbonate — that flags whether unmeasured acids or other anions have accumulated in the blood.

The ankle-brachial index is a simple, non-invasive ratio that compares blood pressure at the ankle to blood pressure at the arm — and it's one of the most widely used screening tools for peripheral artery disease.

The APACHE II score turns a snapshot of a patient's first 24 hours in intensive care into a single number that reflects how critically ill they are.

The Apgar score is the standard first assessment of a newborn's condition, recorded by the attending clinician at 1 minute and 5 minutes after birth.

APRI — the AST to Platelet Ratio Index — is a simple, biopsy-free score built from two routine lab values that can flag liver fibrosis or cirrhosis.

Draw length is one of the two measurements — along with draw weight — that determine whether a bow fits you.

Army Directive 2026-13 now uses waist-to-height ratio (WHtR) as the sole Army body-composition assessment.

The Army Fitness Test (AFT) became the Army's physical fitness test of record on 1 June 2025, replacing the Army Combat Fitness Test (ACFT).

Arterial (or vascular) age reframes cardiovascular risk as an age instead of a percentage — a way of saying 'your combined risk factors look like those of a person this many years older than you, if that older person had ideal levels of everything else.' This calculator builds that estimate from a published, point-based cardiovascular risk model.

The AST/ALT ratio — also known as the De Ritis ratio — divides two liver enzymes to reveal a pattern, not just a level.

Blood Alcohol Concentration (BAC) measures the percentage of alcohol in the bloodstream, determined by drink volume, alcohol percentage, body weight, biological sex, and metabolic elimination rate.

Benzodiazepines vary enormously in potency by weight — a milligram of alprazolam is not comparable to a milligram of diazepam.

The bicarbonate deficit is a weight-based estimate of how much sodium bicarbonate would be needed to raise a patient's serum HCO3 from its current value to a target value.

Biological age measures how old your body functions compared to the population average for your years — giving you a more actionable health picture than the date on your birth certificate alone.

The biophysical profile (BPP) is an antepartum test that combines four ultrasound observations of fetal activity with the non-stress test to assess fetal wellbeing.

The Bishop score grades how ready the cervix is for induction of labor using five findings from a routine cervical exam.

Blood donation eligibility guidelines establish minimum donor age, body weight, hemoglobin levels, and safety deferral intervals required by the FDA and Red Cross for whole blood and apheresis donations.

The concentration of glucose (sugar) in the blood, measured in mg/dL. Normal fasting glucose is 70–99 mg/dL. Consistently elevated blood glucose is diagnostic of diabetes or prediabetes.

Blood pressure is one of the most important vital signs your doctor measures at every visit — and for good reason.

Blood glucose is reported in two different units depending on where you are: mg/dL in the United States, and mmol/L almost everywhere else.

Blood type follows clean Mendelian inheritance patterns established by Karl Landsteiner's 1900 discovery.

Estimated total blood volume is a reference figure used in transfusion medicine and fluid management, most often to calculate allowable blood loss or guide replacement volumes.

Body Mass Index (BMI) is a screening metric derived from a person's weight divided by the square of their height, used to categorize body weight and assess weight-related health risk.

Body mass index (BMI) is calculated the same way for children as for adults — weight divided by height squared — but a single BMI number cannot be read the same way for a child.

BMI is calculated the same way at any age — weight divided by height squared — but for a teenager that raw number means little on its own.

The number of calories your body burns at rest to maintain basic life functions like breathing, circulation, and cell production. BMR is the largest component of daily energy expenditure.

The BODE Index is a validated prognostic tool for chronic obstructive pulmonary disease (COPD), combining four independent domains — Body-mass index, airflow Obstruction, Dyspnea, and Exercise capacity — into a single 0-10 point score.

Body Adiposity Index is a body-fat estimate built from just two measurements — hip circumference and height — with no weight, age, or sex required.

Body fat percentage represents the proportion of total body weight composed of adipose tissue relative to lean mass such as muscle, bone, and organs.

Body frame size is a traditional, easy-to-measure way of estimating overall bone structure — small, medium, or large — using nothing more than your height and wrist circumference.

"Body recomposition" — losing fat and building muscle at the same time — sounds too good to be true, but it's genuinely supported by exercise science.

Body Roundness Index is a body-shape metric that uses your waist and height to estimate how much fat you carry — especially the central, abdominal fat most tied to health risk.

Body-shape typing — Pear, Apple, Hourglass, Rectangle — is a popular, easy way to describe how your waist, hip, and bust measurements relate to one another.

Body surface area is one of the most useful single numbers in clinical medicine.

The BUN/creatinine ratio is a simple bedside calculation — blood urea nitrogen divided by serum creatinine — that helps clinicians distinguish prerenal azotemia from intrinsic renal disease when kidney function tests are abnormal.

Burnout was formally recognized by the World Health Organization in ICD-11 (2019) as an occupational phenomenon — not a personal failing or weakness.

Caffeine is the most widely consumed psychoactive substance in the world, used daily by roughly 90% of Americans.

A unit of energy. In nutrition, the term usually refers to a kilocalorie (kcal) — the energy needed to raise 1 kilogram of water by 1 degree Celsius. Used to measure the energy content of food.

A calorie deficit is the single non-negotiable requirement for fat loss — but how large the deficit is, how it's structured, and how you protect muscle during it determines whether the weight you lose is actually fat.

The Calories Burned Calculator uses the MET framework to translate your body weight, activity choice, duration, and intensity into a concrete calorie and fat-burn estimate — helping you plan workouts, track deficits, and compare activities side by side.

Carbohydrate is the body's most flexible fuel — vital for endurance athletes, optional in very small amounts for keto dieters, and somewhere in between for everyone else.

The Calvert formula doses carboplatin to a target exposure (AUC) rather than by body surface area, which is why it needs an accurate glomerular filtration rate.

Cardiac index takes the single most important number in hemodynamics — how much blood the heart pumps per minute — and corrects it for the one variable that makes raw comparisons misleading: body size.

Cardiac output is the single number that captures how much blood the heart delivers to the body each minute — the product of how much it ejects per beat and how often it beats.

Most sore throats are viral and resolve without antibiotics, but distinguishing a viral sore throat from group A streptococcal pharyngitis by symptoms alone is unreliable.

Cerebral perfusion pressure (CPP) is the single number neurocritical care teams watch most closely after a severe brain injury — it captures, in one value, whether the brain is getting enough blood flow despite whatever is happening to intracranial pressure.

This calculator turns a series of timestamped cervical exams into a rate of change (cm/hr) and compares that rate to labor-progress benchmarks by parity.

Atrial fibrillation is the most common sustained cardiac arrhythmia, affecting more than 30 million people worldwide, and it carries a four-to-five-fold increase in the risk of ischemic stroke.

Child development milestone tracking monitors pediatric gross motor, fine motor, communication, and cognitive milestones across age intervals based on CDC and AAP developmental guidelines.

The Child-Pugh score (formally the Child-Turcotte-Pugh score) grades the severity of liver cirrhosis using five simple clinical and laboratory measures.

Cholesterol lipids (HDL and LDL) are essential fatty compounds in the bloodstream evaluated in lipid panels to screen cardiovascular disease and arterial plaque risk.

The cholesterol ratio, or TC/HDL ratio, is a simple screening figure that combines total cholesterol and HDL cholesterol from the same lipid panel into one number.

Lab reports show cholesterol and triglyceride results in one of two units depending on where you live: mg/dL in the United States, or mmol/L almost everywhere else.

Conception is possible during only about six days of every menstrual cycle — a narrow window that most people cannot pinpoint without understanding their own cycle.

The anion gap is a quick screening calculation, but it has a blind spot: it depends heavily on serum albumin, which is never directly included in the formula.

Total serum calcium readings are influenced by how much albumin is in the blood, because roughly 40% of calcium circulates bound to albumin.

After a platelet transfusion, the raw rise in platelet count depends heavily on the patient's size and how many platelets were transfused — so a bigger patient given a smaller dose can look like a 'poor responder' even with a completely normal transfusion response.

A raw reticulocyte percentage can be misleading in anemia, because it is a percentage of a shrunken red-cell pool rather than an absolute count.

When blood glucose is high, the measured serum sodium can look falsely low. This calculator applies the two published corrections — Katz (1.6) and Hillier (2.4) — to estimate the true sodium once glucose is accounted for, and shows both side by side so no single convention is silently assumed.

Clinicians frequently need to switch a patient between corticosteroids — moving from IV to oral therapy, changing agents for a different mineralocorticoid profile, or adjusting a taper.

Creatine is one of the most heavily-researched sports supplements, yet the dosing question — load or don't load, how much, how long — gets rehashed endlessly in forums and marketing copy.

Creatinine clearance is one of the oldest and most clinically durable kidney estimates.

Crown-rump length (CRL) is the single most accurate way to date a pregnancy. Measured on a first-trimester ultrasound and run through the Robinson & Fleming (1975) regression, it estimates gestational age to within about 3-5 days — tighter than dating by last menstrual period.

Community-acquired pneumonia ranges from mild illness treatable at home to a life-threatening emergency requiring intensive care.

Cycling performance comes down to a competition between the power you can produce and the forces working against you — aerodynamic drag, gravity, and rolling resistance.

After 12 months of dual antiplatelet therapy (DAPT) following coronary stenting, clinicians and patients face a decision: stop therapy at 12 months, or continue it for an extended period.

Not every breath a person takes contributes to gas exchange. Some of it fills the airways without ever reaching functioning alveoli, and some reaches alveoli that have no blood flow to pick up the CO2.

FINDRISC (the Finnish Diabetes Risk Score) estimates a person's 10-year risk of developing type 2 diabetes using eight simple questions — no blood draw required.

Diabetic ketoacidosis (DKA) is a life-threatening complication of diabetes marked by hyperglycemia, ketone-body production, and metabolic acidosis.

Over-the-counter pain relievers and fever reducers are among the most widely used medications in the world, yet dosing errors — too much, too soon, or the wrong medication for the situation — are a leading cause of preventable adverse drug events.

A drug's half-life determines how quickly it leaves the body, how long a single dose keeps working, and how long it takes for repeated dosing to reach a stable blood level.

An estimated due date (EDD) predicts the date of childbirth, calculated as 280 days (40 weeks) from the first day of the last menstrual period (LMP) using Naegele’s rule or ultrasound dating.

The Duke Treadmill Score is one of the most extensively validated tools in cardiology for estimating prognosis after an exercise stress test.

Estimated Glomerular Filtration Rate (eGFR) is a clinical kidney function test calculating blood filtration efficiency per minute from serum creatinine, age, and sex.

Ejection fraction is one of the most widely quoted numbers in cardiology — the percentage of blood the left ventricle pumps out with each heartbeat.

Sweat carries away more than water — it also removes sodium and, to a lesser extent, potassium.

Epinephrine treats two very different emergencies — anaphylaxis and cardiac arrest — with different routes, different concentrations, and different dosing math.

The Epworth Sleepiness Scale (ESS) is one of the most widely used tools for screening general daytime sleepiness.

This calculator does one thing: it converts between an A1c percentage and the estimated average glucose (eAG) it corresponds to, in either direction, using the ADA-endorsed ADAG regression.

Accurately estimating blood loss at delivery matters because clinicians who rely on unaided visual estimation routinely underestimate hemorrhage, delaying recognition and response.

Estimated blood volume (EBV) is a reference figure used across neonatal, pediatric, and adult transfusion medicine to guide fluid resuscitation, transfusion thresholds, and allowable blood loss calculations.

Estimated Energy Requirement is the Institute of Medicine's standardized formula for how many calories a person needs each day to maintain their current weight, based on age, sex, weight, height, and physical activity level.

Estimated fetal weight (EFW) converts four routine ultrasound measurements into a predicted weight in grams.

EtG (ethyl glucuronide) urine testing can detect alcohol consumption long after the alcohol itself has cleared the bloodstream, which is why it's used in workplace, legal, probation, and treatment-program settings.

This calculator estimates your face shape from four simple measurements — forehead, cheekbone, and jawline width, plus face length — comparing their ratios against the classification rules commonly used in hairstyle and eyewear guides.

The Fagerström Test for Nicotine Dependence is a brief, six-item questionnaire that scores how physically dependent a smoker is on nicotine, from 0 (minimal) to 10 (severe).

FENa is one of the oldest and most widely used bedside tests in nephrology: a single paired serum-and-urine sample, plugged into a simple ratio, that helps separate two very different causes of a rising creatinine — reduced blood flow to otherwise-healthy kidneys (prerenal azotemia) versus direct injury to the kidney tissue itself (intrinsic AKI, most often acute tubular necrosis).

Female fertility follows a well-documented decline with age, shaped by falling egg quantity and quality.

The period during a menstrual cycle when conception is possible, typically spanning 5 days before ovulation and the day of ovulation itself.

An estimated fetal weight on its own doesn't say much — 1,800 grams is unremarkable at 36 weeks but a significant growth concern at 30 weeks.

FEUrea (fractional excretion of urea) is a diagnostic index that helps distinguish prerenal azotemia — a volume-responsive drop in kidney function — from intrinsic acute kidney injury, using paired serum and urine urea nitrogen and creatinine values.

The FEV1/FVC ratio is the single most important number in a spirometry report — it is the first screen that separates a normal breathing pattern from an obstructive one.

Fat-Free Mass Index (FFMI) scales a person's lean body mass to their height to evaluate muscular development independently of adipose tissue.

Fresh frozen plasma (FFP) is dosed by body weight, using a standard reference range rather than a single fixed volume.

The FIB-4 index combines age, two liver enzymes, and platelet count into a single non-invasive score that estimates the probability of advanced liver fibrosis.

Most Americans eat about half the fiber they need — roughly 15 g/day against a recommended 25–38 g.

Fish oil labels can be confusing: the front of the bottle advertises a total fish oil milligram count (like "1000 mg fish oil"), but the omega-3s doing the work — EPA and DHA — are listed separately on the Supplement Facts panel, often at far lower amounts.

The Framingham Risk Score turns a handful of lab values into a single actionable number: your probability of a major heart event in the next decade.

Most of the testosterone in blood is bound to carrier proteins and isn't immediately usable by tissues.

The free water deficit estimates how much free water is needed to correct hypernatremia — an elevated serum sodium — by bringing the concentration back down to a normal target.

The highest average power (in watts) a cyclist can sustain for approximately one hour. Used to set training zones for cycling. FTP is typically measured with a 20-minute all-out effort and multiplied by 0.95.

Fundal height is one of the simplest, lowest-cost screening checks in prenatal care — a tape-measure reading compared against a rule of thumb.

Gabapentin is unusual among common neuropathic-pain and anticonvulsant medications: it is not metabolized by the liver at all.

The GAD-7 is the most widely-used brief anxiety screening tool in primary care and mental health settings.

Body Mass Index is calculated the same way at every age — weight divided by height squared — but the range considered "healthy" is not fixed.

Pregnancy can be dated three ways in routine and fertility care: from the last menstrual period, from a known conception or ovulation date, or from an IVF embryo transfer date.

The Glasgow Coma Scale (GCS) is the most widely used bedside tool for quantifying a patient's level of consciousness after brain injury, stroke, or acute illness.

A class of medications (such as semaglutide/Ozempic and tirzepatide/Mounjaro) that mimic the GLP-1 hormone to suppress appetite, slow gastric emptying, and regulate blood sugar. Used for type 2 diabetes and weight loss.

GLP-1 medicines like Wegovy, Ozempic, Zepbound, and Mounjaro are not started at their full dose.

“Do I qualify for a GLP-1?” usually comes down to one FDA rule and a short list of health conditions.

GLP-1 medications like Ozempic, Wegovy, and Zepbound produce rapid weight loss — but not all of that loss is fat.

Glucose infusion rate (GIR) tells clinicians, in a single weight-normalized number, how much glucose an infant or child is receiving per minute from IV dextrose or parenteral nutrition.

Blood glucose is reported in two different units depending on where you are: mg/dL in the United States, and mmol/L almost everywhere else.

The glycemic index ranks carbohydrate-containing foods by how quickly they raise blood glucose, on a 0-100 scale anchored to pure glucose.

Glycemic load (GL) estimates how much a food or meal is likely to raise blood sugar by combining two pieces of information: the food's glycemic index (how fast its carbs act) and the actual amount of carbohydrate in the serving eaten.

This calculator turns a calorie deficit into a plain-English timeline: given your current weight, your goal weight, and how much you're cutting from maintenance calories, it estimates how many weeks — and roughly what calendar date — you'd reach your goal.

The GRACE ACS risk score turns eight routine admission measurements into an estimate of how likely a patient with acute coronary syndrome is to die in hospital and over the following months.

Grip strength has become a popular longevity headline, but the number on its own doesn't mean much without context.

Group B Streptococcus (GBS) is a common, usually harmless bacterium that can be passed from parent to newborn during labor, occasionally causing serious infection.

GTPAL is a standard shorthand used in prenatal and labor & delivery charting to summarize a patient's pregnancy history in a few characters: Gravida, Term, Preterm, Abortions, and Living.

The Gupta MICA calculator turns five preoperative variables into a continuous, statistically derived estimate of how likely a patient is to suffer a myocardial infarction or cardiac arrest within 30 days of noncardiac surgery.

Anticoagulation prevents stroke in atrial fibrillation but inherently raises bleeding risk.

A hormone produced by the placenta shortly after embryo implantation, typically detectable 8–10 days after fertilization. Rising HCG levels double approximately every 48–72 hours in early pregnancy.

The healthy weight range is the span of body weight that keeps your BMI inside the standard "normal weight" band of 18.5 to 24.9.

Training intensity ranges defined as percentages of maximum heart rate. Zones range from Zone 1 (recovery, 50-60%) to Zone 5 (maximum effort, 90-100%).

The HEART score is one of the most widely used and best-validated clinical decision tools for chest pain in the emergency department.

The Heaviness of Smoking Index (HSI) is a fast, 2-item screen for nicotine dependence, built from just two everyday habits: how many cigarettes someone smokes per day, and how soon after waking they light the first one.

"How tall will my child be?" is one of the most common questions parents ask — and the honest answer is a range, not a number.

HOMA-IR estimates insulin resistance from a single fasting blood draw, using just two numbers: fasting glucose and fasting insulin.

Heart Rate Variability (HRV) measures the variation in time between consecutive heartbeats (RMSSD), serving as an objective biomarker for autonomic nervous system balance and recovery.

Water makes up roughly 60% of adult body weight and is involved in virtually every physiological process, from regulating body temperature and lubricating joints to transporting nutrients and flushing metabolic waste.

Ibuprofen is one of the two most common OTC fever and pain relievers given to children, but it is dosed differently depending on fever severity, capped in two separate ways, and restricted below 6 months of age.

The ICH Score is the most widely used bedside grading scale for spontaneous intracerebral hemorrhage, combining five variables available within minutes of a head CT into a single number that correlates strongly with 30-day mortality.

A target weight range based on height, frame size, and sex. Calculated using formulas like Devine, Hamwi, Robinson, or Miller — each producing slightly different results.

Implantation is the moment a fertilized egg burrows into the uterine lining, triggering the hormonal cascade that sustains a pregnancy.

The Injury Severity Score (ISS) is one of the most widely used anatomical trauma severity scores in emergency medicine and trauma research.

The International Normalized Ratio (INR) standardizes prothrombin time results so that a clotting-time measurement from one lab means the same thing as a measurement from another lab using a different reagent.

The insulin correction factor (also called the insulin sensitivity factor, or ISF) estimates how far one unit of insulin is expected to lower blood glucose.

This calculator estimates a starting total daily insulin dose from body weight and insulin sensitivity, then splits it into basal (long-acting) and bolus (mealtime) insulin and divides the bolus across meals.

Intermittent fasting is an eating pattern cycling between designated periods of voluntary fasting and calorie consumption (such as 16/8 or 5:2 schedules).

The Ganzoni equation estimates the total amount of elemental iron a patient needs to correct iron deficiency, combining the iron required to rebuild circulating hemoglobin with the iron needed to refill the body's depot stores.

Calculating an intravenous infusion rate is one of the most fundamental — and most frequently tested — skills in nursing.

IVF pregnancies use a different dating method than natural conception — one anchored to the precise transfer date rather than an estimated last period.

Intravenous immunoglobulin (IVIG) is dosed very differently depending on why it's being given — a monthly antibody-replacement infusion for immunodeficiency looks nothing like a single 2 g/kg loading dose for Kawasaki disease.

A metabolic state in which the body primarily burns fat for fuel, producing ketone bodies, due to very low carbohydrate intake (typically under 50g/day). The goal of the ketogenic diet.

Kt/V is the standard yardstick for how much a hemodialysis session actually cleared.

The exercise intensity at which blood lactate begins to accumulate significantly. Training at or slightly above this point is highly effective for improving endurance performance. Closely related to FTP in cycling.

Most lipid panels report an LDL cholesterol value that was never directly measured — it was calculated from total cholesterol, HDL, and triglycerides using the Friedewald formula, published in 1972 and still the default method used by most clinical laboratories.

Low-density lipoprotein — the primary carrier of cholesterol in the blood and the main contributor to plaque buildup in arteries. Optimal LDL is below 100 mg/dL; above 160 mg/dL is considered high.

Lean body mass is the meaningful denominator for most fitness and nutrition calculations.

Levothyroxine is the standard treatment for hypothyroidism, and getting the starting dose right matters: too low and the patient stays symptomatic for longer than necessary, too high (especially in older or cardiac patients) can precipitate angina or arrhythmia.

Lidocaine's maximum safe dose depends on two things at once: body weight, and whether epinephrine is present.

When a pleural effusion is sampled by thoracentesis, the first and most important question is whether it is a transudate or an exudate — the answer determines whether the workup continues (exudate) or stops once the systemic cause is addressed (transudate).

The Lille model answers a specific, high-stakes question: after a week of corticosteroids for severe alcoholic hepatitis, is this treatment working?

This tool computes the maximum safe single dose of lidocaine, bupivacaine, ropivacaine, or mepivacaine from a patient's body weight, plain or with a vasoconstrictor, to help avoid local anesthetic systemic toxicity (LAST).

Total lung capacity (TLC) is one of the core measurements in a pulmonary function test, but a raw liter value only means something in the context of what's expected for a person's height and sex.

The percentage of daily calories derived from protein, carbohydrates, and fat. A standard balanced diet might be 20% protein / 50% carbs / 30% fat; a keto diet might be 5% carbs / 25% protein / 70% fat.

The three main categories of nutrients the body needs in large amounts: protein, carbohydrates, and fat. Each provides energy (4 cal/g protein and carbs, 9 cal/g fat).

Maddrey's discriminant function is a simple bedside formula, built from two routinely-drawn labs, that flags the alcoholic hepatitis patients most likely to benefit from corticosteroid therapy.

The Holliday-Segar method is the standard formula for estimating a pediatric patient's baseline intravenous fluid needs from body weight alone.

This calculator adds up the calories (and, optionally, the protein/carbs/fat) of every food item on your plate so you get one meal total instead of adding numbers by hand.

Mean airway pressure (MAP) summarizes an entire ventilator breath cycle — peak pressure, floor pressure, and timing — into a single number that correlates closely with oxygenation and barotrauma risk.

Mean arterial pressure is the single number that best captures the pressure actually pushing blood into your organs.

In the earliest days of a confirmed intrauterine pregnancy — before an embryo is large enough to see or measure — sonographers date the pregnancy and screen for concerning findings using the gestational sac itself.

Melatonin is one of the most widely used sleep supplements, but a single "right dose" doesn't exist — the amount and timing that make sense for falling asleep at a normal bedtime are different from what's commonly cited for jet lag or for sleeping during the day after a night shift.

The legacy MELD-Na score turns four routine lab values into a single educational reference number for liver-disease severity and short-term risk.

Menopause is a normal biological transition, but its timing, duration, and symptom severity vary enormously between women.

The Mentzer index is a simple bedside ratio — MCV divided by RBC count — that helps separate two common causes of microcytic anemia: thalassemia trait and iron deficiency anemia.

A unit expressing the energy cost of physical activities relative to resting metabolic rate. Sitting = 1 MET; brisk walking = 3.5 METs; running at 6 mph = 10 METs. Used to estimate calorie burn.

Metabolic syndrome is not a single disease you either have or don't — it's a cluster of 5 measurable risk factors that, together, signal a substantially higher risk of type 2 diabetes, heart disease, and stroke than any one factor alone.

The Modified Early Warning Score (MEWS) turns five routine bedside observations into a single number that flags hospitalized patients who may be deteriorating.

The amount of each vitamin and mineral your body needs isn't one fixed number — it depends on your age, your sex, and, for women, whether you're pregnant or breastfeeding.

Morphine milligram equivalents let clinicians and pharmacists compare, and sum, opioid regimens that mix several different drugs.

The NAFLD fibrosis score turns six routine clinical and laboratory values into a single number that estimates the probability of advanced liver fibrosis in patients with nonalcoholic fatty liver disease.

Service members are tested on physical readiness on a recurring cycle, and the score decides far more than bragging rights — it feeds promotion boards, special-duty eligibility, and retention.

Net carbs is the number most keto and low-carb dieters track instead of total carbohydrates, because it tries to estimate only the carbs that meaningfully raise blood sugar.

The neutrophil-lymphocyte ratio (NLR) is a simple lab-derived ratio — the absolute neutrophil count divided by the absolute lymphocyte count — used as a general marker of systemic inflammation.

Nearly every newborn develops some degree of jaundice in the first week of life, and most of it is harmless.

NEWS2 (National Early Warning Score 2) converts seven routine vital-sign observations into a single 0-19 score used across NHS wards and ambulance services to catch acute deterioration early.

The NIH Stroke Scale is the most widely used clinical instrument for quantifying the severity of an acute stroke.

Nuchal translucency screening is one of the most common first-trimester ultrasound measurements, and it's easy to leave the appointment with a number and no context for what it means.

One-Repetition Maximum (1RM) is the maximal amount of weight an athlete can lift for a single repetition of a resistance exercise through a full range of motion.

Switching a patient from one opioid to another — an opioid rotation — is one of the higher-risk routine tasks in pain and palliative care.

The osmolal gap compares a lab-measured serum osmolality against a value calculated from routine labs.

This calculator classifies your Body Mass Index (BMI) into the six adult weight-status tiers defined by the World Health Organization — from Underweight through Obesity Class III.

The release of a mature egg from an ovary, typically occurring mid-cycle (around day 14 of a 28-day cycle). The fertile window spans approximately 6 days surrounding ovulation.

The Oxygenation Index (OI) combines three numbers clinicians already track at the bedside — FiO2, mean airway pressure, and PaO2 — into a single value that grades how hard the lungs and the ventilator are working together to oxygenate the blood.

Pace is the rate of travel in distance-based athletics expressed as elapsed duration per unit of distance (such as minutes per mile or minutes per kilometer).

A unit measuring cumulative tobacco exposure. One pack year = smoking one pack (20 cigarettes) per day for one year. A 30-pack-year history significantly increases lung cancer and COPD risk.

Hospitalized medical patients face a meaningfully elevated risk of venous thromboembolism (VTE) from a combination of illness, inflammation, and reduced mobility — but not every patient needs pharmacologic prophylaxis, which carries its own bleeding risk.

The PaO2/FiO2 (P/F) ratio is the bedside oxygenation measurement clinicians use to stage the severity of acute respiratory distress syndrome (ARDS) under the Berlin Definition.

This calculator applies the Parkland (Baxter) formula to estimate the intravenous fluid a burn patient needs in the first 24 hours, and splits it into the two timed windows the protocol specifies.

Peak expiratory flow (PEF) is one of the simplest ways to track how well air moves through the lungs, and it's central to most asthma action plans.

The Pearl Index expresses a contraceptive trial's raw pregnancy count as a single annualized rate — unintended pregnancies per 100 woman-years of exposure.

Children are not small adults — a dose that is safe for a 40 kg child can be an overdose for a 12 kg toddler.

Few numbers reassure and confuse parents in equal measure like a growth percentile.

Weight-based (mg/kg) dosing keeps a child's medication proportional to their size — but a purely linear formula has no upper bound.

The menstrual cycle is one of the most important indicators of reproductive health.

The PHQ-9 is the most widely-used brief depression screening tool in primary care, mental health, and research settings.

Calculated plasma osmolality estimates the concentration of dissolved particles in blood from three routine labs — sodium, glucose, and BUN — without waiting for a send-out osmometer result.

Plasma volume is the liquid, cell-free portion of total blood volume — the complement to red cell volume.

The Pneumonia Severity Index turns 20 routine findings — age and sex, nursing-home residence, five comorbidities, five exam abnormalities, and seven lab or radiographic results — into a 30-day mortality risk class for adults with community-acquired pneumonia.

Ponderal Index divides mass by height cubed instead of height squared, the way BMI does.

Potassium is an essential electrolyte most adults in the United States do not get enough of.

One of three periods dividing pregnancy: first (weeks 1-12), second (weeks 13-26), and third (weeks 27-40). Each trimester involves distinct developmental milestones.

Pregnancy weight gain guidelines establish recommended maternal weight increases by trimester based on pre-pregnancy Body Mass Index (BMI) to support fetal development and maternal health.

This calculator screens for well-documented risk factors for spontaneous preterm birth — a birth before 37 weeks — using a transparent, additive checklist rather than a single validated predictive score.

Protein is the most important macronutrient for body composition, yet most people either drastically undereat it or worry unnecessarily about eating too much.

The protein/creatinine ratio (PCR) is a same-unit comparison of urine protein to urine creatinine from a single spot sample that approximates 24-hour urine protein excretion without requiring a timed collection.

qSOFA (quick SOFA) is a fast, lab-free bedside score introduced by the Sepsis-3 consensus definitions to help clinicians outside the ICU — in the emergency department, on a general ward, or in pre-hospital settings — quickly flag patients with suspected infection who may be at higher risk of a poor outcome.

The QT interval on an ECG shortens and lengthens with heart rate even in perfectly healthy hearts, which makes the raw QT interval hard to compare across patients or across readings taken at different heart rates.

QUICKI turns two routine fasting labs — glucose and insulin — into a single number that estimates how sensitive your body is to insulin.

The Rapid Shallow Breathing Index (RSBI), also called the Tobin index, is one of the most widely used bedside predictors of ventilator weaning readiness in critical care.

Rate-pressure product (RPP) is one of the simplest hemodynamic indices in cardiology: multiply heart rate by systolic blood pressure and you get a workable estimate of how hard the heart muscle is working.

The red cell indices — MCV, MCH, and MCHC — turn three raw complete blood count numbers into a size-and-color profile of the average red blood cell.

Recovery time between workouts is one of the most under-appreciated variables in training.

Relative Fat Mass (RFM) is a simple, formula-based estimate of whole-body fat percentage that only needs your height and waist circumference.

The number of times the heart beats per minute when completely at rest. Normal resting heart rate is 60–100 bpm; trained athletes often have resting rates of 40–60 bpm. A lower rate generally indicates better cardiovascular fitness.

The reticulocyte production index (RPI) refines a routine anemia workup by correcting the reticulocyte percentage for both the severity of anemia and how long reticulocytes spend maturing in peripheral blood.

The Revised Geneva Score estimates how likely a patient is to have a pulmonary embolism before any diagnostic test is run, using eight clinical findings that can all be measured or observed directly.

The Revised Trauma Score (RTS) condenses three vital signs — level of consciousness, blood pressure, and breathing rate — into a single physiologic severity score for trauma patients.

The number of steps taken per minute while running. An optimal cadence of ~170–180 steps per minute reduces injury risk by shortening ground contact time.

The shock index is a simple bedside ratio — heart rate divided by systolic blood pressure — that can reveal hemodynamic instability before it shows up in either vital sign alone.

The SIRS (Systemic Inflammatory Response Syndrome) criteria were the first widely adopted bedside tool for recognizing systemic inflammation, and for two decades they formed the backbone of how sepsis was defined and diagnosed.

The six-minute walk test (6MWT) is a simple, low-cost way to measure how far someone can walk in six minutes — a widely used proxy for functional exercise capacity.

The skinfold method estimates body fat percentage from a handful of caliper measurements of subcutaneous fat thickness at specific body sites.

Sleep cycle calculations determine optimal bedtimes and wake times based on 90-minute sleep cycles (NREM and REM), preventing grogginess caused by waking during deep slow-wave sleep.

Sleep debt is the gap between the sleep you need and the sleep you actually get, and it compounds faster than most people expect.

The body begins recovering from smoking almost immediately after the last cigarette, and that recovery continues, in well-documented stages, for more than a decade.

Recovery is not a single event — it is a cascade of biological, psychological, and financial changes that unfold across minutes, days, months, and years.

Correcting hyponatremia too quickly is one of the few harms in medicine that's almost entirely preventable by pacing the plan correctly.

The sodium deficit calculation is a standard first step in planning sodium replacement for hyponatremia: it converts a lab value gap (current sodium vs.

Nutrition labels list sodium in milligrams, but home cooks usually measure salt by weight or by the teaspoon.

Daily sodium intake tracking compares dietary sodium consumption against the recommended guideline of less than 2,300 milligrams per day.

The Sequential Organ Failure Assessment (SOFA) score is a validated intensive-care tool that grades dysfunction across six organ systems — respiratory, coagulation, liver, cardiovascular, central nervous system, and renal — and sums them into a single 0-to-24 score.

The Sokolow-Lyon index is one of the oldest and most widely used ECG-based screening tools for left ventricular hypertrophy (LVH) — a simple sum of two voltage measurements that can be read directly off a standard 12-lead ECG.

A "standard drink" is a fixed amount of pure alcohol that lets you compare a can of beer, a glass of wine, and a shot of spirits on the same scale — but the size of that fixed amount is not the same in every country.

Step counting is one of the most accessible ways to track daily physical activity, yet most people underestimate how significantly body weight, pace, terrain, and walking style affect calorie burn.

Obstructive sleep apnea (OSA) affects an estimated 936 million adults globally yet remains undiagnosed in up to 80% of cases.

The Stress Cost Calculator turns a handful of inputs into a result you can act on.

Stroke volume is the amount of blood the left ventricle ejects with a single heartbeat — the building block that, multiplied by heart rate, gives cardiac output.

Getting your supplement doses right means balancing evidence-based RDAs against your individual factors — age, sex, pregnancy status, and health goals.

Swim pace is more nuanced than running or cycling pace because it varies by stroke, pool length, open versus closed water, and the presence of turns.

Target heart rate training zones define optimal aerobic and anaerobic exertion ranges based on resting heart rate, maximum heart rate, and training intensity percentage using the Karvonen formula.

Total Daily Energy Expenditure (TDEE) is the total number of calories a body burns in a day, combining basal metabolic rate with physical activity and the thermic effect of feeding.

The energy expenditure required to digest, absorb, and metabolize food. Protein has the highest TEF (20–30%), carbohydrates moderate (5–10%), and fat the lowest (0–3%). TEF accounts for ~10% of TDEE.

Lung-protective ventilation doses tidal volume against ideal body weight rather than actual weight, because lung size scales with height and sex, not with adiposity.

The TIMI risk score for ST-elevation myocardial infarction (STEMI) is a bedside tool that converts 8 pieces of information already available at presentation into a single 0-14 number estimating 30-day mortality risk.

The TIMI risk score is a widely used bedside tool for stratifying patients with unstable angina or non-ST-elevation myocardial infarction (UA/NSTEMI).

Total body water (TBW) is the largest single component of body composition, typically 50–65% of an adult's weight.

Alteplase (tPA) dosing for acute ischemic stroke is weight-based but strictly capped, and the total dose is always split into a bolus and an infusion.

Transferrin saturation (TSAT) is a simple ratio calculated from two common lab values — serum iron and total iron binding capacity (TIBC) — that gives a fast snapshot of how saturated the blood's iron-transport system is.

The transtubular potassium gradient (TTKG) is a bedside index clinicians have used to estimate whether the kidney's potassium-secreting response to hyperkalemia or hypokalemia is appropriate.

The urea reduction ratio (URR) is a simple, widely used bedside measure of hemodialysis adequacy — how effectively a dialysis session removed urea, a marker waste product, from the blood.

The urine anion gap is a quick screening calculation from a random or spot urine sample — urine sodium plus urine potassium minus urine chloride — used to help localize the cause of a non-anion-gap metabolic acidosis.

This calculator estimates the probability of a successful vaginal birth after cesarean (VBAC) using a published logistic-regression model from the Maternal-Fetal Medicine Units (MFMU) Network.

This calculator estimates the vital capacity (VC) expected for someone of a given age, height, and sex, using a classic predicted-VC regression from pulmonary physiology.

Vitamin A intake is uniquely confusing to track because two different units — RAE and IU — coexist on food and supplement labels, and the conversion between them depends on whether the vitamin A came from an animal or plant source.

Vitamin C is a water-soluble antioxidant vitamin that the body can't produce or store in large amounts, so it needs a steady daily supply from food or supplements.

Vitamin D deficiency affects an estimated one billion people globally, driven by indoor lifestyles, northern latitudes, and the melanin that protects darker skin from UV damage.

Vitamin D deficiency affects an estimated one billion people globally, driven by indoor lifestyles, northern latitudes, and the melanin that protects darker skin from UV damage.

VLDL cholesterol is rarely measured directly on a standard lipid panel — instead, it is estimated from triglycerides using a simple formula.

VO2 Max is the maximum volume of oxygen an individual can transport and utilize during incremental, high-intensity aerobic exercise, measuring cardiovascular fitness.

VO2 max — your body's maximum oxygen uptake — is the most widely studied marker of aerobic fitness and one of the strongest predictors of long-term health.

Waist-to-height ratio (WHtR) assesses cardiometabolic and abdominal visceral fat risk by dividing waist circumference by height, where a ratio under 0.50 indicates lower health risk.

Waist-hip ratio is one of the simplest and most predictive measures in cardiometabolic medicine.

Warfarin dosing is adjusted based on how a patient's INR compares to their target range, using standardized percentage-adjustment nomograms developed by anticoagulation clinics.

Dietary water intake measures the hydration contributed by moisture-rich foods such as fruits and vegetables, which typically supply ~20% of daily fluid intake.

The recommended daily amount of water a person should consume. Varies by body weight, activity level, climate, and health conditions. General guideline is about 8 cups for adults.

This calculator turns two weigh-ins — a starting weight and a current weight — into a single percentage that shows how much of your starting body weight you've lost.

Points-based food tracking condenses calories, protein, sugar, and saturated fat into a single number, making it faster to compare foods at a glance than reading four separate label fields.

Venous thromboembolism (VTE) — encompassing both deep vein thrombosis (DVT) and pulmonary embolism (PE) — affects approximately 900,000 Americans annually and remains a leading cause of preventable in-hospital death.

The Wilks coefficient is a strength standard formula used to normalize and compare powerlifting performance across athletes of differing bodyweights.

Winters' formula predicts the expected respiratory compensation for a primary metabolic acidosis, letting clinicians check whether a patient's measured pCO2 reflects appropriate compensation or signals a second, concurrent acid-base disorder.

The 4T score is the most widely used bedside tool for estimating the pretest probability of heparin-induced thrombocytopenia (HIT) — a serious, immune-mediated adverse reaction to heparin that causes thrombocytopenia and a sharply increased risk of new thrombosis.