BMI for Teens Calculator

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Walk-through

How to Use This Calculator

3 steps

1

Enter the teen's sex, age, weight, and height

Select sex, enter age in years and months (12 years 0 months through 19 years 0 months), then enter weight and height in either metric (kg/cm) or imperial (lb/in) units. The result updates instantly as you type.

2

Read the BMI-for-age percentile

The headline result is a percentile, not a raw BMI number — it compares this teen's BMI to CDC growth-chart data for others of the same age and sex, then names the weight-status category (Underweight, Healthy weight, Overweight, or Obese) that percentile falls into.

3

Check the BMI and Category tabs for context

The BMI tab shows exactly how the raw BMI value was computed from weight and height. The Category tab lists all four CDC weight-status bands with this teen's current band highlighted, so you can see how close the result is to a neighboring category.

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Reference

Formula & Methodology

2 formulas

BMI

BMI = weight (kg) / height (m)²

The same BMI formula used at any age — weight in kilograms divided by height in metres, squared. Imperial inputs (lb/in) are converted to kg/cm before this step.

BMI-for-age percentile (CDC LMS method)

z = ((BMI / M)^L − 1) / (L × S); percentile = Φ(z) × 100

L, M, and S are age- and sex-specific parameters from the CDC Growth Charts (2000) BMI-for-age reference tables, looked up for the teen's exact age in months (linearly interpolated between whole-month table entries). Φ is the standard normal cumulative distribution function. The percentile places this teen's BMI within the CDC reference population of the same age and sex — it is the same method used by this site's Growth Percentile calculator, restricted here to the BMI-for-age measure and the 12–19 age window.

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YMYL

Trust, Methodology & Sources

Reviewed by Calculover Editorial Team · Updated 2026-07-23 · 2 sources

Editorial accountability

Author: Calculover Editorial Team - Editor

Owner: Calculover Editorial Team - Editorial owner

Reviewer: Calculover Editorial Team - Clinical content reviewer

Last reviewed: 2026-07-23

Last verified: 2026-07-23

Data effective: 2026-07-23

Methodology

The BMI for Teens Calculator computes BMI = weight (kg) / height (m)^2, then converts that BMI into a percentile using the CDC Growth Charts (2000) BMI-for-age LMS method: z = ((BMI / M)^L - 1) / (L x S), percentile = normal-CDF(z) x 100, where L, M, and S are age- and sex-specific parameters looked up (with linear interpolation between whole-month table entries) for the teen's exact age in months. The percentile is classified into four CDC weight-status categories: Underweight (below 5th percentile), Healthy weight (5th-85th), Overweight (85th-95th), and Obese (95th percentile and above). This calculator is scoped to ages 12 years 0 months through 19 years 0 months; the underlying reference table and z-score method are the same ones used by this site's Growth Percentile calculator, sourced from the same CDC Growth Charts (2000) BMI-for-age dataset.

Assumption: Weight and height are measured accurately for the same individual, with the correct unit system selected before reading the result.

Assumption: The user wants a screening estimate of BMI-for-age percentile against the general U.S. teen population, not a personalized clinical growth assessment.

Assumption: Age is entered precisely in years and months, since the CDC reference table is indexed by month and the percentile can shift noticeably within a single age-year.

Limitations & guidance

BMI-for-age percentile does not measure body fat, muscle mass, or body composition directly — it only compares a weight-to-height ratio against a reference population of the same age and sex.

The CDC Growth Charts (2000) reference data were collected primarily from national surveys conducted before 1980 and may not reflect the full diversity of body types, ethnicities, or growth patterns in today's population.

This calculator does not account for individual factors such as pubertal stage, ethnicity, muscle mass from athletic training, or underlying medical conditions, all of which a clinician would weigh alongside a percentile.

A single percentile from one measurement is a snapshot, not a trend — tracking growth over multiple visits gives a pediatrician far more useful information than an isolated result.

Professional guidance: The BMI for Teens Calculator is for general health education and screening only. It is an estimate, not a diagnosis, and it is not medical advice or a substitute for assessment, diagnosis, or treatment by a pediatrician or other qualified healthcare professional. Do not make medical decisions based on its output.

Primary sources

Centers for Disease Control and Prevention. Body Mass Index (BMI): Child and Teen BMI Categories. - CDC

Kuczmarski RJ, et al. 2000 CDC Growth Charts for the United States: Methods and Development. National Center for Health Statistics. - CDC / National Center for Health Statistics

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Glossary

Key Terms Explained

6 terms

BMI-for-age A BMI value interpreted relative to a reference population of the same age and sex, rather than against fixed adult cutoffs. Because typical body composition changes throughout childhood and puberty, the same raw BMI number can mean something different at age 12 than at age 18.

Percentile The percentage of teens of the same age and sex in the CDC reference population whose BMI is at or below this teen's BMI. A 75th percentile means this teen's BMI is higher than roughly 75 out of 100 same-age, same-sex peers in the reference data.

CDC growth chart A set of reference curves published by the U.S. Centers for Disease Control and Prevention, built from national survey data collected mostly before 1980, describing typical growth patterns for children and teens ages 2 through 19 in the United States.

Adolescent BMI BMI-for-age percentile calculated for the 12–19 age range specifically — the period spanning puberty, when growth rate and body composition change more than at any other point after infancy.

Weight status category The CDC's four-band classification of BMI-for-age percentile: Underweight (below the 5th percentile), Healthy weight (5th to 85th), Overweight (85th to 95th), and Obese (95th percentile and above).

Growth reference The underlying dataset (here, the CDC Growth Charts 2000 LMS parameters) that defines what a 'typical' BMI trajectory looks like by age and sex, against which an individual measurement is compared.

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Scenarios

Real-World Examples

3 worked examples

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13-year-old

A 13-year-old boy who is 155 cm tall and weighs 45 kg

Sex Male Age 13 years 0 months Weight 45 kg Height 155 cm

His BMI works out to about 18.7. Against CDC data for 13-year-old boys, that lands in the healthy-weight band, roughly in the middle of the typical range — not close to either the overweight or underweight cutoffs. Weight and height are the two inputs that move this result the most; age matters too, since the same BMI reads differently a year or two later.

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17-year-old

A 17-year-old girl who is 163 cm tall and weighs 68 kg

Sex Female Age 17 years 0 months Weight 68 kg Height 163 cm

Her BMI works out to about 25.6. Against CDC data for 17-year-old girls, that percentile falls in the overweight band (85th–95th percentile) rather than obese — it's a reminder that BMI-for-age uses different cutoffs than the fixed adult BMI scale, where 25.6 alone would already be labeled overweight by a wider margin.

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Percentile bands explained

Why the same BMI can fall in different categories at different ages

Underweight Below 5th percentile Overweight 85th–95th percentile

Because the reference curve shifts with age and sex, a BMI of 21 might be at the 60th percentile for a 12-year-old but the 40th percentile for an 18-year-old of the same sex, since typical BMI rises through the teen years as part of normal growth. That's the entire reason percentile-based bands exist instead of one fixed adult cutoff: a single BMI number can't tell you where a still-growing teen stands without knowing their age and sex too.

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Deep Dive

Understanding the BMI for Teens Calculator

3 chapters · 4 min read

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. This calculator converts a teen's BMI into a percentile against CDC growth-chart data for others of the same age and sex, then reports the weight-status category that percentile falls into. It's built for parents, teens, and anyone who wants the same screening estimate a pediatrician's office would compute.

How the BMI for Teens Calculator works

The calculator first computes a standard BMI from weight and height, converting imperial units to metric internally. It then looks up the age- and sex-specific L, M, and S reference parameters from the CDC Growth Charts (2000) BMI-for-age table for the teen's exact age in months, interpolating between the table's whole-month entries. Those parameters feed the LMS z-score formula, and the z-score is converted to a percentile using the standard normal distribution. This is the same method the CDC's own pediatric BMI tools use, and the same underlying reference table this site's Growth Percentile calculator draws on — restricted here to the BMI-for-age measure and the 12–19 age window that most closely matches how 'BMI for teens' is typically searched and used.

Inputs and what they mean

Sex and age matter as much as weight and height here, because the reference curve a BMI is compared against depends on both. Age must be entered precisely — years and months — since the CDC reference table is indexed by month, and a percentile computed for '15 years old' can shift meaningfully between 15 years 0 months and 15 years 11 months. Weight and height can be entered in either metric or imperial units; switching units mid-session automatically converts the values already entered rather than clearing them.

Limits and edge cases

This calculator only accepts ages from 12 years 0 months through 19 years 0 months; outside that window it points to the Growth Percentile calculator (for younger children) or the standard adult BMI calculator (for ages 20 and up) instead of returning a misleading number. BMI-for-age percentile is a population screening tool, not a diagnosis — it says nothing directly about body composition, muscle mass, or health status, and puberty timing varies enough between individuals that two teens at the same percentile can look very different physically. A pediatrician who can examine growth history over time, not a single percentile snapshot, is the right resource for any specific concern.

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Questions

Frequently Asked Questions

6 questions

How is this different from adult BMI?+

Adult BMI is read against fixed cutoffs (for example, 25 and above is 'overweight' for every adult, regardless of age or sex). Teen BMI-for-age instead converts the same BMI formula's result into a percentile against CDC reference data for teens of the same age and sex, because typical body composition shifts substantially during growth and puberty. The same BMI value can land in different weight-status categories depending on whether the person is 13 or 18.

What age range does this cover?+

This calculator is scoped to ages 12 years 0 months through 19 years 0 months. For children younger than 12, use the Growth Percentile calculator, which covers ages 0–19 across weight, height, BMI, and head circumference. For ages 20 and up, use the standard adult BMI calculator instead.

How accurate is this calculator?+

It uses the CDC Growth Charts (2000) LMS reference parameters and the standard LMS z-score-to-percentile method, the same approach used in clinical pediatric BMI tools. It's accurate as a screening estimate against that reference population, but it is not a diagnosis and doesn't account for individual factors like build, ethnicity, or specific health conditions that a clinician would consider.

Does puberty timing affect the result?+

The CDC reference curves already account for typical variation in growth and body composition across the 12–19 age range, since they're built from a population that includes teens at many different pubertal stages. Still, puberty timing varies a lot between individuals, so a percentile from a single measurement is best read as one data point rather than a complete picture — a pediatrician tracking growth over multiple visits has more context than this calculator can.

What units does it use?+

Weight can be entered in kilograms or pounds, and height in centimetres or inches — use the unit toggle to switch, and previously entered values convert automatically. Age must be entered as whole years plus 0–11 extra months.

Is this medical advice?+

No. This calculator is for general education and screening only. It is not a diagnosis and does not replace an assessment by a pediatrician or other qualified healthcare professional. Do not make medical decisions based solely on its output.

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