Child BMI Calculator — BMI Percentile for Children
BMI
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Approximate Percentile
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Weight Category
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Understanding Child BMI
Unlike adult BMI, children's BMI must be interpreted using age and sex-specific percentiles because body composition changes as children grow. The CDC provides growth charts for children ages 2-20 that account for these normal developmental changes.
Categories: underweight (below 5th percentile), healthy weight (5th to 84th), overweight (85th to 94th), and obese (95th percentile and above). A child at the 60th percentile has a higher BMI than 60% of children their age and sex.
BMI percentile is a screening tool, not a diagnostic measure. Active, muscular children may have a high BMI without excess fat. A healthcare provider should evaluate BMI alongside other factors like growth patterns, diet, activity level, and family history.
Frequently Asked Questions
Why are percentiles used instead of BMI categories?
Children's body fat changes with age and differs between boys and girls. A BMI of 18 might be healthy for one age but overweight for another. Percentiles compare a child to others of the same age and sex.
At what percentile should I be concerned?
Discuss with your pediatrician if your child is below the 5th or above the 85th percentile, or if there are sudden changes in percentile. A single reading is less meaningful than tracking trends over time.
Is child BMI accurate?
BMI is a useful screening tool but not a direct measure of body fat. Very athletic children may have high BMI due to muscle. Your pediatrician can assess body composition more accurately if needed.