BMI Calculator
Check your body mass index from height and weight.
Ratio to the upper healthy limit (25).
Weight ÷ height³ — less skewed by height than BMI.
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | 40.0 and above |
How to use it
- 1Choose metric (cm, kg) or imperial (ft/in, lb) units.
- 2Enter your height and weight.
- 3Read your BMI on the color-coded gauge, its category, and the healthy weight range for your height.
- 4Scroll down for BMI Prime, your Ponderal Index, and the full WHO category table.
Example
At 170 cm and 70 kg: BMI = 70 ÷ (1.70 × 1.70) = 24.2, which falls in the “Normal weight” range — a BMI Prime of 0.97 and a Ponderal Index of 14.2 kg/m³.
How it works
Body mass index is weight divided by height squared: BMI = weight (kg) ÷ height (m)². In imperial units, it's BMI = 703 × weight (lb) ÷ height (in)². The standard WHO categories are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30+ obese, split into Class I, II, and III. Outside the normal range, the calculator also shows how much weight would bring you to a BMI of 24.9. BMI doesn't distinguish muscle from fat, so it's a general screening measure, not a full diagnosis — the Ponderal Index (weight ÷ height³) is shown alongside it as a less height-sensitive alternative.