Understanding your BMI
1. BMI formula
BMI = weight (kg) ÷ height (m)²
2. BMI categories
| Category | WHO international | Asian standard |
|---|---|---|
| Underweight | < 18.5 | < 18.5 |
| Normal weight | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 24.9 |
| Obese | ≥ 30.0 | ≥ 25.0 |
3. Example
Someone 170 cm tall weighing 65 kg has a BMI of 65 ÷ (1.70 × 1.70) ≈ 22.5: normal weight under both the WHO and the Asian standard.
Frequently asked questions
Why are there two BMI standards?
Studies show Asian populations face higher risks of diabetes and heart disease at lower BMI levels. The WHO Western Pacific region and the International Diabetes Institute therefore suggest lower cut-offs for Asians: overweight from 23 and obese from 25, instead of 25 and 30.
Is BMI accurate?
BMI is a quick screening tool, not a diagnosis. It does not distinguish muscle from fat, so very muscular people may score high, and it does not apply to children, teenagers or pregnant women.
What is a healthy weight for my height?
The calculator shows the weight range that gives a BMI in the normal band for your height under the chosen standard.