Child BMI Calculator
Calculate BMI and estimate BMI-for-age percentile for children and teens using age, sex, height, and weight.
Results
This calculator provides an estimated screening result only. Child BMI should be interpreted with official age- and sex-specific growth charts, growth history, puberty stage, health history, and a clinician’s judgment. It does not diagnose a medical condition.
Use this Child BMI Calculator to calculate BMI and estimate BMI-for-age percentile for children and teens using age, sex, height, and weight.
Unlike adult BMI, child and teen BMI is interpreted according to age- and sex-specific percentiles because BMI changes during growth and development.
Calculation Method
For metric units:
BMI = weight (kg) ÷ height (m)²
For pounds and inches:
BMI = weight (lb) ÷ height (in)² × 703
After BMI is calculated, it is compared with BMI-for-age reference data for children of the same age and sex.
Common CDC screening categories for ages 2–19 are:
- Underweight: below the 5th percentile
- Healthy weight: 5th to below the 85th percentile
- Overweight: 85th to below the 95th percentile
- Obesity: 95th percentile or higher
Example
Suppose a 10-year-old boy weighs 75 lb and is 55 inches tall.
BMI = (75 ÷ 55²) × 703
BMI ≈ 17.4
The BMI is then compared with BMI-for-age reference data for a 10-year-old boy to estimate the percentile and screening category.
Important Limitations
BMI is a screening measure and does not directly measure body fat or diagnose a health condition. A child’s growth history, puberty, nutrition, activity, medical history, and other clinical factors may affect interpretation.
This type of BMI-for-age assessment is intended for children and teens ages 2 through 19 years. Concerns about a child’s weight or growth should be discussed with a pediatric healthcare professional.