About the BMI Calculator
Calculate your body mass index from your height and weight in metric or imperial units. See your WHO category and the healthy weight range for your height.
Key features
- BMI from metric (cm, kg) or imperial (ft, in, lb) input
- WHO adult weight category
- Healthy weight range for your height
- Visual BMI scale
- Private: nothing leaves your browser
- Results update as you type
Body Mass Index for adults
BMI is a quick screening measure that relates your weight to your height. It's widely used by doctors and public health bodies to flag possible weight-related health risks. It's a starting point for a conversation, not a diagnosis.
Formula
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²
Example: 70 kg and 175 cm → 70 ÷ (1.75 × 1.75) = 22.9 (normal weight). The healthy range for 175 cm is about 56.7–76.3 kg.
WHO adult BMI categories
| BMI | Category |
|---|---|
| Below 16 | Severe thinness |
| 16 – 16.9 | Moderate thinness |
| 17 – 18.4 | Underweight (mild thinness) |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight (pre-obese) |
| 30 – 34.9 | Obesity class I |
| 35 – 39.9 | Obesity class II |
| 40 and above | Obesity class III |
Limitations of BMI
- Muscle vs fat: athletes may have a high BMI with low body fat.
- Fat distribution: belly fat carries more risk; check your waist-to-height ratio (aim for under 0.5).
- Age, sex and ethnicity: the same BMI can mean different body-fat levels.
- Pregnancy: BMI doesn't apply.
This tool is for general information only and isn't medical advice. Talk to a healthcare professional about your weight and health.
Related calculators
Estimate body composition with the Body Fat Calculator, find a target with the Ideal Weight Calculator, or plan your intake with the Calorie Calculator.
How to use the BMI Calculator
- Enter your numbers in the fields above. Units and options can be changed at any time.
- The result updates instantly as you type; there's no calculate button to press.
- Check the breakdown under the main result for the details behind the number.
- Adjust the inputs to compare scenarios, for example a different rate or term.