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BMI Calculator
Calculate your Body Mass Index and see where you fall on the WHO classification scale. No sign-up, no paywall.
What is BMI?
Body Mass Index (BMI) is a number that relates weight and height to estimate whether a person is in a healthy weight range. It was developed by Belgian mathematician Adolphe Quetelet in the 19th century and is the screening tool most widely used by the WHO (World Health Organization) for population assessment. BMI is a screening tool — it does not replace a medical evaluation.
How to use this calculator
Enter your height in centimeters (e.g. 170 for 1.70 m) and your weight in kilograms. The result appears automatically along with its classification. Best for adults aged 18-65. Don't use it for children, pregnant women, or athletes with high muscle mass — BMI can give misleading results in those cases.
How BMI is calculated
The formula is simple: BMI = weight (kg) ÷ height² (m). For example, someone weighing 70 kg at 1.70 m has BMI = 70 ÷ (1.70 × 1.70) = 24.2. The result is interpreted using the WHO classification table below.
BMI classification table
| Classification | BMI range |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5 — 24.9 |
| Overweight | 25.0 — 29.9 |
| Obesity Class I | 30.0 — 34.9 |
| Obesity Class II | 35.0 — 39.9 |
| Obesity Class III | ≥ 40.0 |