BMI Calculator for Children & Teens
Calculate BMI for children and teens ages 2-20 using CDC growth chart percentiles. BMI in children is age and gender-specific.
CDC Weight Categories for Children
Underweight (< 5th percentile)
Below healthy range — consult a pediatrician
Healthy Weight (5th – 84th percentile)
Normal, age-appropriate weight
Overweight (85th – 94th percentile)
Above healthy range for age and sex
Obese (≥ 95th percentile)
Well above healthy range — seek medical guidance
Frequently Asked Questions
Why is BMI calculated differently for children?
Unlike adults, children's body composition changes as they grow. BMI in children is interpreted using age- and sex-specific percentiles from CDC growth charts, because a "healthy" BMI value varies by age. A BMI of 18 might be normal for a 10-year-old but underweight for a 16-year-old.
What do the BMI percentiles mean?
BMI percentiles show how a child's BMI compares to other children of the same age and sex. For example, a child at the 60th percentile has a higher BMI than 60% of children their age and sex. The CDC classifies: <5th = underweight, 5th-84th = healthy weight, 85th-94th = overweight, ≥95th = obese.
Is BMI accurate for athletic children?
BMI can overestimate body fat in children who are very muscular and underestimate it in children who have lost muscle mass. It is a screening tool, not a diagnostic measure. A pediatrician can provide a more thorough assessment using skinfold measurements or other methods.
What age range does this calculator cover?
This calculator covers children and teens ages 2 to 20 years. For children under 2, weight-for-length charts are used instead of BMI. For adults over 20, use the standard adult BMI calculator.