Calculate your child's BMI and CDC percentile for age. For children ages 2-20. Enter age, sex, height, and weight.
Body Mass Index (BMI) for children and teens is calculated the same way as adults — weight divided by height squared — but interpreted differently using age- and sex-specific percentiles from the CDC growth charts.
Unlike adults, where a BMI of 25+ is overweight for everyone, children's healthy BMI ranges change as they grow. A 5-year-old and a 15-year-old with the same BMI can be in completely different weight categories. That's why BMI-for-age percentile is used instead of raw BMI.
This calculator is designed for children ages 2 to 20. It computes BMI from height and weight, then provides an estimated weight status category based on CDC percentile ranges: underweight (<5th), healthy weight (5th-84th), overweight (85th-94th), or obese (≥95th). Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Childhood obesity is a growing health concern. Early identification of unhealthy weight trends allows for lifestyle interventions before problems escalate. This calculator gives parents a quick way to check their child's BMI status between well-child visits. Having a precise figure at your fingertips empowers better planning and more confident decisions.
BMI = (Weight in lbs × 703) / (Height in inches)² Weight Categories (CDC): <5th percentile = Underweight 5th–84th = Healthy Weight 85th–94th = Overweight ≥95th = Obese
Result: BMI 15.7 — Healthy Weight (~55th percentile)
An 8-year-old boy who is 51 inches tall and weighs 58 lbs has a BMI of 15.7. For boys at age 8, a BMI of 15.7 falls near the 55th percentile — well within the healthy weight range (5th-84th percentile).
Adult BMI categories are fixed: 18.5-24.9 is normal for all adults. Child BMI categories shift with age and sex because body composition changes during growth. A BMI of 18 might be healthy at age 10 but underweight at age 16.
The CDC recommends WHO growth charts for children 0-2 and CDC charts for ages 2-20. BMI-for-age uses CDC charts, which are based on US children surveyed before the obesity epidemic peaked, providing a historical reference.
BMI doesn't differentiate between muscle and fat. An athletic child with more muscle mass may have a higher BMI but be perfectly healthy. Always consider BMI alongside physical activity levels, diet quality, and overall health.
Children's body fat changes as they grow, and boys and girls develop differently. BMI-for-age percentiles account for these variations by comparing a child's BMI to other children of the same age and sex.
A healthy BMI-for-age is between the 5th and 84th percentile. Below 5th is underweight, 85th-94th is overweight, and 95th or above is classified as obese by the CDC.
BMI can overestimate body fat in muscular children and underestimate it in less active ones. It's a screening tool, not a diagnosis. Your pediatrician may use additional measurements like skinfold thickness for a more complete assessment.
BMI-for-age charts begin at age 2. For younger children, weight-for-length is used instead. Talk to your pediatrician about which growth measures are appropriate for your child's age.
Never restrict a child's diet without medical guidance. Focus on whole foods, active play, reduced screen time, and family meals. Your pediatrician can create an appropriate plan if weight management is needed.
BMI-for-age percentiles do account for normal changes during puberty since the reference data includes children going through puberty. However, rapid body composition changes during puberty can make single BMI readings less meaningful.