BMI Calculator
BMI = kg / m². US units convert with 1 lb = 0.45359237 kg and 1 in = 0.0254 m. Informational, not a medical diagnosis.
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How to calculate BMI
- Choose metric (cm, kg) or US (feet, inches, pounds).
- Enter height and weight.
- Read BMI, WHO adult category, healthy-weight range for that height, and both unit systems.
- This is not for children and is not a diagnosis.
Body mass index
kg / m² with WHO adult labels
| Formula | mass in kg ÷ (height in m)² |
|---|---|
| Underweight | BMI under 18.5 |
| Healthy weight | 18.5 to under 25 |
| Overweight | 25 to under 30 |
| Obesity | 30 and above |
What BMI is
Body mass index is mass in kilograms divided by height in meters squared. US units convert with 1 lb = 0.45359237 kg and 1 in = 0.0254 m, then use the same formula. Categories on this page are WHO adult cutoffs: under 18.5 underweight, 18.5 to under 25 healthy weight, 25 to under 30 overweight, 30 and above obesity.
Metric and US inputs
Metric is centimeters and kilograms. US is feet, inches, and pounds. Inches of 12 or more are added into the total height. For a height-only conversion use the height converter.
Not a diagnosis
BMI does not measure fat, muscle, or health by itself. Athletes can have a high BMI with low fat. Children, pregnancy, and some ethnic-specific charts use other cutoffs. This page does not apply those. See a clinician for a decision that affects care. The disclaimer applies.