Adult BMI categories
For adults aged 20 years and older.
| BMI (kg/m²) | Level |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to <25.0 | Normal weight |
| 25.0 to <30.0 | Overweight |
| 30.0 to <35.0 | Obesity class I |
| 35.0 to <40.0 | Obesity class II |
| 40.0 or more | Obesity class III |
Metric inputs · WHO references
WHO-aware BMI calculator for Kenya
Calculate BMI from weight and height, then apply the correct WHO reference for adults, children, and adolescents instead of using adult cut-offs for everyone.
Enter your measurements
Use kilograms and centimetres. Age and the WHO reference chart determine how the result is interpreted.
Enter body weight in kilograms.
Use standing height for adults.
Age
WHO child references cover 0-60 months and 61-228 months. The calculator accepts adults from 20 years.
Select the chart that matches the child. This is required because WHO growth references differ by sex.
Your BMI result
Calculating…
BMI
kg/m²
Assessment
- Reference
- WHO z-score
- Measurement used
Enter your details to calculate BMI
The result will use the correct WHO reference for the selected age.
Important: BMI is a screening measure, not a diagnosis. It can require different interpretation for pregnancy, athletes, and some medical conditions.
Pregnancy: this is not a pregnancy weight-gain calculator. Use pre-pregnancy BMI and gestational guidance from a qualified healthcare professional.
How this calculator works
BMI is weight in kilograms divided by height in metres squared. The calculation is simple; the interpretation changes with age and the WHO reference system.
WHO references used
Adults use standard categories. Ages 61-228 months use WHO 2007 BMI-for-age z-scores. Ages 0-60 months use weight-for-length/height, with length below 24 months and standing height from 24 months.
When to seek advice
If a result concerns you, or a child’s growth is changing quickly, discuss it with a healthcare professional. A single BMI result does not assess health on its own.
WHO BMI categories and levels
Use the table for the selected age group to see where the result falls. Adults use BMI ranges in kg/m². Children and adolescents use age- and sex-specific WHO z-scores, so a child’s raw BMI must not be judged using adult cut-offs.
After calculation, the matching level is highlighted below.
WHO BMI-for-age levels for children aged 61-228 months (5-19 years)
For children aged 61-228 months, this is the WHO 5-19 years reference. The level is based on the child’s age- and sex-specific BMI-for-age z-score.
| WHO z-score | Level |
|---|---|
| Below -3 SD | Severe thinness |
| -3 to below -2 SD | Thinness |
| -2 to +1 SD | Within reference range |
| Above +1 to +2 SD | Overweight |
| Above +2 SD | Obesity |
WHO weight-for-length/height levels for children under 5 years
Use recumbent length below 24 months and standing height from 24 through 60 months.
| WHO z-score | Level |
|---|---|
| Below -3 SD | Severe wasting |
| -3 to below -2 SD | Wasting |
| -2 to +1 SD | Within reference range |
| Above +1 to +2 SD | At risk of overweight |
| Above +2 to +3 SD | Overweight |
| Above +3 SD | Obesity |
BMI and growth-chart results are screening information, not a diagnosis. A healthcare professional should interpret a child’s growth over time, measurements, health, and development together.
Sources: WHO adult BMI ranges · WHO BMI-for-age, 5-19 years · WHO weight-for-length/height · WHO under-five guidance
BMI calculator questions
Short answers about the reference used for each age group.
Does this BMI calculator use adult cut-offs for children?
No. Adults use standard BMI categories. Children and adolescents use the selected WHO age- and sex-specific reference, while children under five use WHO weight-for-length or weight-for-height assessment.
Why does the calculator ask for age and a WHO reference chart?
BMI interpretation changes with age and sex during growth. Age selects the WHO reference system and the chart selection selects the official boys or girls reference data.
Can I use this BMI calculator during pregnancy?
This calculator is not a pregnancy weight-gain tool. Pregnancy weight guidance should use pre-pregnancy BMI and gestational-age recommendations from a qualified healthcare professional.
What are the WHO BMI levels for adults and children?
Adults use BMI ranges. Children aged 61-228 months (the WHO 5-19 years reference) use age- and sex-specific BMI-for-age z-scores, while children aged 0-60 months use weight-for-length or weight-for-height z-scores. The matching table below the calculator shows the categories and levels.