Calculate your body mass index (BMI) using metric (kg, cm) or imperial (lb, ft/in) measurements. Your result appears instantly alongside the WHO reference category. Free, no login.
Select your preferred unit system — metric or imperial — using the toggle at the top of the calculator. Enter your height and weight. BMI updates immediately as you type.
The result includes your numeric BMI and the corresponding WHO category (Underweight, Normal weight, Overweight, or Obese). No data is stored or sent anywhere — the calculation happens entirely in your browser.
Weight: 80 kg · Height: 180 cm (1.80 m)
BMI = 80 ÷ (1.80 × 1.80) = 80 ÷ 3.24
BMI = 24.7 — Normal weight
Weight: 176 lb · Height: 5 ft 11 in
Converted: 79.8 kg · 180.3 cm → BMI = 79.8 ÷ 3.25
BMI = 24.5 — Normal weight
| BMI range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (Class I) |
| 35.0 – 39.9 | Obese (Class II) |
| 40.0 and above | Obese (Class III) |
BMI is a population-level screening tool. It is calculated from height and weight only, so it cannot distinguish between fat mass and muscle mass. A person with significant muscle (such as someone doing resistance training or on TRT) may have a BMI in the "overweight" range while carrying very little excess body fat.
BMI also does not account for fat distribution. Two people with the same BMI can have very different risk profiles depending on where their body fat is stored. Use BMI as a rough indicator, not a complete picture of body composition or health.