BMI Percentile (Child) Calculator

About this calculator

A child's BMI-for-age percentile shows where their body mass index falls relative to other children of the same age and sex, using growth-chart reference curves like those published by the CDC (for U.S. children, ages 2-20) or the WHO (for younger children internationally) — unlike adult BMI, which uses fixed cutoffs (18.5, 25, 30), children's BMI must be interpreted relative to a growth curve because what's ‘normal’ body composition changes dramatically as kids grow. A child at the 85th percentile has a BMI higher than 85% of same-age, same-sex peers in the reference population.

Pediatricians and school health screenings use BMI-for-age percentile as one screening tool for weight-related risk, with published clinical cutoffs typically defining underweight as below the 5th percentile, healthy weight as the 5th to 85th percentile, overweight as the 85th to 95th percentile, and obesity as at or above the 95th percentile — though pediatric guidelines stress that percentile alone shouldn't drive a diagnosis without a full clinical evaluation, since growth patterns, timing of puberty, and body composition vary widely among healthy children.

This calculator takes a child's age, sex, height, and weight and estimates where their BMI falls on the growth curve — an approximation intended for general reference, not a substitute for an official pediatric growth chart or clinical assessment.