Kids BMI Calculator
A free BMI calculator for kids and teens (2–20 years). Compute BMI and the CDC BMI-for-age percentile—the standard approach for a kids BMI calculator using U.S. reference data.
Plain-language interpretation
BMI alone does not describe body composition. For children, the percentile shows where BMI sits relative to CDC reference peers. Category labels (underweight, healthy weight, overweight, obesity ranges) follow CDC percentile cutoffs and remain reference language only.
Formula and data standard
BMI = weight(kg) / height(m)². Percentile from CDC 2000 BMI-for-age LMS tables (bmiagerev). Extended BMI-for-age (2022) is not applied in v1.
Applicable age range
2–20 years.
Worked example
A boy at Agemos 120.5 with height 140 cm and weight 35 kg has BMI ≈ 17.9. Using the CDC male BMI LMS row at 120.5 yields a z-score near 0.53 and a percentile near the 70th—within the healthy weight reference range by CDC cutoffs.
Limitations
- 2000 charts may characterize very high BMI less well than Extended BMI charts.
- Does not assess muscle mass, puberty stage, or clinical risk factors.
- Not diagnostic or prescriptive.
References
FAQ
- Why is a BMI calculator for kids different from adult BMI?
- For children and teens, BMI is interpreted with age- and sex-specific percentiles (BMI-for-age), not fixed adult cutoffs alone.
- What does a kids BMI calculator result mean?
- You get BMI in kg/m², a BMI-for-age percentile, and a CDC reference category label. These are educational references, not a diagnosis.
Content maintenance date: 2026-07-16. Editorial and methodology review: see Editorial and methodology review.