BMI Calculator for Children and Teens
Calculate BMI-for-age for children and teenagers — using growth chart percentiles and healthy ranges.
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BMI Calculator for Children and Teens Calculating BMI for children uses the same formula as for adults — weight (kg) divided by height (m) squared — but the number is interpreted differently. Instead of fixed WHO cutoffs, children's BMI is compared to a reference population using growth chart percentiles. A BMI value that's healthy for a 14-year-old may be overweight for a 6-year-old. --- See our complete guide to health calculators and the BMI calculator guide for adult BMI context. Why Children's BMI Uses Percentiles? Children's bodies change dramatically between ages 2 and 18. Average BMI dips in early childhood (around ages 4–6), then rises again in what clinicians call the "adiposity rebound." A BMI of 18 is normal for a 10-year-old but underweight for a 17-year-old. Fixed adult…
Frequently Asked Questions
How is BMI calculated for children differently?
Children use the same BMI formula as adults (weight in kg / height in m²), but the result is interpreted using age- and sex-specific percentile charts rather than fixed cutoffs. A BMI of 20 means very different things for a 6-year-old vs. a 16-year-old. The CDC publishes the reference growth charts used in the US.
What is a healthy BMI for children?
Healthy weight for children is defined as BMI-for-age between the 5th and 85th percentile. Below the 5th percentile is underweight; 85th to 95th percentile is overweight; 95th percentile and above is obese. These percentile thresholds come from the 2000 CDC Growth Charts.
What is BMI percentile for kids?
BMI percentile compares a child's BMI to a reference population of children the same age and sex from the CDC's 2000 growth chart dataset. A child at the 60th percentile has a BMI higher than 60% of same-age peers — within the healthy range. The percentile is more informative than the raw BMI number for children.
At what age is adult BMI applicable?
The WHO and CDC apply adult BMI classifications (with fixed 18.5/25/30 cutoffs) starting at age 20. For ages 2–19, BMI-for-age percentile is used instead. Some practitioners use adult cutoffs for 18–19 year olds, but CDC guidelines recommend percentile-based interpretation through age 19.
How do I interpret BMI charts for children?
Find your child's age on the horizontal axis and BMI on the vertical axis of a BMI-for-age chart. The percentile curve the point falls on is their BMI percentile. Healthy weight: 5th–85th percentile. The CDC provides interactive charts and a BMI calculator at cdc.gov/bmi. Regular tracking over time is more informative than any single measurement.
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