Math for the everyday-everything.
Tips, recipes, fuel cost, pet ages, travel budget, reading time, solar savings, time zones — the calculators that come up between meetings and the grocery store.
No ads · No signup · No paywall · Instant results · Always free
Hand-picked starters.
Restaurant math and kitchen ratios.
Tip splits, pizza-party planning, coffee ratios, recipe scaling, and the cooking-time math that decides when dinner's ready.
Tip Calculator
Drag bill, tip %, and diners. Tip amount, total, and per-person split update live.
Pizza Party Planner
Slices needed by appetite, party size, and slices-per-pizza. No more "we ran out" or "we have 4 boxes left."
10 pies25 adults · 3 slices eachAges, dates, and pet years.
Age calculator, date duration, time zones, plus the pet-age conversions and feeding math for your dog or cat.
Age Calculator
Drag the birth year. Years lived + months + days since last birthday update live.
Dog Age Calculator
Updated 2019 UCSD epigenetic formula — far more accurate than "1 dog year = 7 human years."
~52 human yrs7-year-old medium dogBigger than one calculator? Follow the flow.
Multi-step paths that string the right daily life tools together in the order most people actually use them — with your numbers carried from step to step.
Fuel, costs, and car-decision math.
MPG and fuel-cost math, gas-vs-electric comparisons, lease-vs-buy, depreciation, and the trip-cost numbers behind a long drive.
MPG Calculator
Drag miles driven and gallons used. MPG plus $/mile (at current gas prices) update live.
Gas vs Electric
$/mile comparison: gas at MPG and current pump price vs. EV at kWh/mile and local electric rate.
EV: $0.04/mivs gas: $0.13/miSolar, energy, and household costs.
Solar savings, LED swaps, laundry energy, pool chemistry, moving costs, and the renovation math before you sign a contract.
Solar Savings
Drag monthly kWh and electric rate. Annual savings, lifetime savings, and CO₂ avoided update live.
LED Savings Calculator
Switch incandescent / CFL to LED — annual electricity savings and replacement-cost payback.
~$10/bulb/yrvs 60W incandescentBooks, shows, weddings, vacations.
Reading time, marathon TV planning, audiobook speed, wedding budget, travel costs, jet lag — every leisure-time math you'd Google.
Reading Time
Drag book pages and your reading speed. Total hours, days at 30 min/day, and audiobook hours update live.
Travel Budget Calculator
Daily budget by destination — flights, hotels, food, activities — built into a per-day spend estimate.
~$150/dayU.S. mid-tierData, speed, units, and currency.
Data unit conversion (B → TB), bandwidth math, password strength, plus the everyday unit and currency converters.
Data Unit Converter
Drag a byte count. KB, MB, GB, TB (binary IEC) update live — and so does the equivalent download time on a 100 Mbps line.
Unit Converter
Universal unit converter — length, weight, temperature, volume, area, energy, and the rare ones.
200+ unitsSI + US + ImperialGolf, music, knitting, and clothing fit.
Golf handicap, BPM lookup, knitting yardage, plus international shoe / ring / bra / clothing size conversion.
Golf Handicap
Drag your score and the course rating. USGA-style handicap index + course-adjusted strokes update live.
Shoe Size Converter
Convert between US, UK, EU, JP, and CN shoe sizes for men, women, and kids.
US 10= UK 9 = EU 43Two good options? See the head-to-head.
The daily life vocabulary, decoded.
Every definition links to the calculator that puts the term to work. Browse the full glossary →
MPG = miles driven / gallons usedFill-up to fill-up fuel economy — the number every trip-cost and gas-vs-electric comparison starts from.Tip per person = bill × tip % / peopleThe restaurant split: total the gratuity first, then divide — rounding per person last keeps the math fair.Energy cost = watts × hours / 1,000 × rate per kWhWhat any appliance actually costs to run — the engine behind LED-swap, laundry, and solar-savings math.Frequently asked questions
Is the dog-age formula really "1 dog year = 7 human years"?
No — that's a myth. The updated 2019 UCSD epigenetic-clock formula gives a much more accurate conversion: human age ≈ 16 × ln(dog age) + 31. By that math, a 1-year-old dog is "biologically ~31"; a 7-year-old dog is ~52. The Dog Age calculator implements both formulas so you can compare.
What tip percentage is standard in the U.S.?
15% is the historical baseline; 18–20% is now expected for table service at most U.S. restaurants. For takeout / counter-service / coffee, 10% is a generous norm but not always expected. The Tip Calculator defaults to 18%, with quick-toggle buttons at 15%, 20%, and 25%.
How accurate is the MPG calculation?
MPG = miles ÷ gallons. The widget shows MPG exactly. The "$/mile" calculation depends on local gas prices, which the slider lets you adjust. Real-world MPG varies ±5–10% from EPA-rated MPG based on driving style, terrain, weight, and weather — the full MPG calculator surfaces those adjustments.
Does Reading Time account for difficulty?
The widget assumes a single WPM rate, which works for general-fiction reading speed. Dense academic / technical reading is closer to 100–150 WPM; light fiction is closer to 300–400 WPM. The full Reading Time calculator lets you pick a difficulty multiplier or auto-detect from book genre.
Why does Solar Savings show such different numbers from quotes I get?
Vendor quotes typically include the 30% federal tax credit, state rebates, and sometimes net-metering credits — which makes the headline payback look shorter. The widget shows the pre-incentive savings; the full Solar Savings calculator lets you toggle incentives and shows both the gross and net payback period.
11 categories, one search box, zero signups. If it has a number, we calculate it.
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