BMI Percentile Calculator for Children — CDC 2000
Enter a child's sex, age, weight and height to get their exact BMI-for-age percentile and z-score from CDC 2000 growth charts. The bell-curve shows where they sit relative to the reference population of the same age and sex.
Sex
years
months
kg
cm
Relative to CDC 2000 reference population of same age and sex
How does this calculator work?
BMI percentile for children uses the CDC 2000 LMS method: calculate BMI = W/H², then z = ((BMI/M)^L−1)/(L×S) using age- and sex-specific L, M, S values, then percentile = Φ(z)×100. CDC categories: underweight <5th, healthy 5th–85th, overweight 85th–95th, obese ≥95th percentile.
Formula
How this is calculated
The CDC 2000 BMI-for-age growth charts were developed from nationally representative US survey data (NHANES I–III) and are the standard reference used by US paediatricians and widely internationally. They express where an individual child's BMI falls among peers of the same age and sex.
The technical method is the LMS (Box-Cox) transformation, which accounts for the fact that BMI distributions are right-skewed and the degree of skewness changes with age. Three smoothed parameters are published at each age-in-months: L (the Box-Cox power correcting for skewness), M (the median BMI) and S (a measure of spread). A z-score is derived as z = ((BMI/M)^L − 1)/(L×S), and that z-score is then converted to a percentile using the standard normal cumulative distribution Φ(z).
CDC defines: underweight as below the 5th percentile; healthy weight as 5th–84th; overweight as 85th–94th; and obese as at or above the 95th percentile. The bell-curve visualisation shows the standard normal distribution, shaded up to the child's z-score — the shaded proportion equals the percentile. LMS values are interpolated linearly between the published monthly/bi-annual anchor points in the CDC tables.
Frequently asked questions
Children's bodies change rapidly and normal BMI values vary by age. A 10-year-old and a 15-year-old with the same BMI number are in very different parts of their growth curves. The percentile tells you where the child stands relative to peers, which is the clinically meaningful figure.
The 85th–94th percentile is classified as overweight by CDC, and 90th is in that range. However, a single measurement is not a diagnosis. Growth trajectory (whether percentile is stable or rising), pubertal stage, muscle mass, family history and activity level all matter. A paediatrician can interpret this in context.
Yes. The CDC 2000 charts remain the US standard for children aged 2–20. For children under 2 the WHO 2006 growth standards are preferred. The WHO also publishes separate growth charts for ages 5–19 used in many other countries.
TG we-Calculate Editorial Team. (2026). BMI Percentile Calculator for Children — CDC 2000 [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bmi-percentile-child-calculator
TG we-Calculate Editorial Team. "BMI Percentile Calculator for Children — CDC 2000." TG we-Calculate. 2026. https://we-calculate.com/calculator/bmi-percentile-child-calculator.
TG we-Calculate Editorial Team, "BMI Percentile Calculator for Children — CDC 2000," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bmi-percentile-child-calculator
@misc{wecalculate_bmi_percentile_child_calculator, title = {BMI Percentile Calculator for Children — CDC 2000}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bmi-percentile-child-calculator}}, year = {2026}, note = {TG we-Calculate} }
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