Health calculator
Child & Adolescent BMI Calculator
Child BMI is not read with adult categories. This tool calculates BMI, then compares it with the WHO BMI-for-age reference for the entered age and sex.
Why child BMI is different
Children and adolescents are still growing. The same BMI can mean different things at different ages and for boys and girls.
This is why adult labels such as “overweight at 23” must not be applied here. Classification depends on BMI-for-age.
How this calculator works
BMI is still calculated as weight (kg) ÷ height (m)².
The category then uses official WHO 2007 BMI-for-age LMS parameters for completed months from 5 years 0 months to 19 years 0 months. The z-score is compared with WHO cut-offs: severe thinness below −3 SD, thinness below −2 SD, normal between −2 SD and +1 SD, overweight above +1 SD, and obesity above +2 SD.
Limitations
One reading does not replace a growth chart reviewed over time, or advice from a doctor, nurse or dietitian.
The tool does not estimate disease risk, school fitness, or takaful eligibility.
Reference categories
| Range | Category |
|---|---|
| < −3 SD | Severe thinness |
| < −2 SD | Thinness |
| −2 SD to +1 SD | Normal |
| > +1 SD | Overweight |
| > +2 SD | Obesity |
Common questions
What age range is supported?
This page uses the WHO Growth Reference 2007 for school-age children and adolescents, covering 5 years 0 months to 19 years 0 months.
Why do I need to enter sex?
WHO BMI-for-age tables are separate for boys and girls. The same BMI can fall into different categories depending on sex and age.