How accurate are these cutoffs?

Interpolated from CDC averages — within ±1 BMI point of the real curve in most ages. Good for a "ballpark" answer; not for medical decisions, which should use actual CDC percentile charts.

My child grew but BMI dropped — should I worry?

Usually not — kids enter growth spurts where height jumps before weight catches up. Persistent rapid drops over months warrant a check-in.

BMI Calculator for Children

Pediatric BMI with rough CDC percentile category for children and teens aged 2–19.

Result

BMI

17.9

Healthy

Healthy weight (5–84th)

Age10 years (boy)
Approx. healthy rangeBMI 15.4 – 19.4
Approx. overweight cutoff (85th %ile)BMI 19.4Borderline
Approx. obesity cutoff (95th %ile)BMI 22.2High risk
NoteInterpolated; not a substitute for CDC chart lookupPediatric — see doctor for actual percentile

How to use this calculator

Use the child's most recent measured weight and height.
Pick the right sex — pediatric BMI cutoffs differ by sex.
A "warning" or "error" badge means see a pediatrician — don't panic; growth varies.
For children under 2, this tool doesn't apply. Weight-for-length is used instead.

About this tool

BMI for children is interpreted differently than for adults — the same number means different things at different ages because kids' body composition changes through growth. Pediatricians use age- and sex-specific percentile charts (CDC in the US, WHO globally) instead of fixed BMI cutoffs. This calculator gives an approximate categorisation by interpolating the 85th and 95th-percentile cutoff curves, which is good enough to know whether a doctor visit is warranted — but not a substitute for an actual percentile lookup at a check-up. For ages under 2, BMI isn't used at all; doctors track weight-for-length instead.

Frequently asked

BMI doesn't distinguish muscle from fat. Athletic kids (especially young teens with broad builds) often score "overweight" by BMI. A pediatrician can do a skinfold check or just eyeball it.