In imperial units, BMI = 703 × weight (lb) ÷ height (in)². For most adults, 18.5–24.9 is the healthy range; under 18.5 is underweight, 25–29.9 overweight, and 30+ obese. BMI is a screening tool — it doesn't distinguish muscle from fat, so very muscular people may read high.
What is BMI?
Body Mass Index (BMI) is a ratio of your weight to your height, used as a quick screening tool for weight status. This calculator lets you enter each measurement in whatever units suit you — centimeters, meters, feet & inches, kilograms, pounds or stone — and even type values directly (try "5'8" or "173 cm"). The marker slides along the healthy-to-obese scale as you go.
How BMI is calculated
The formula is BMI = weight (kg) ÷ height (m)²; other units are converted automatically.
Adult BMI categories
- Underweight: below 18.5
- Healthy weight: 18.5 – 24.9
- Overweight: 25 – 29.9
- Obese: 30 and above
For general information only — not medical advice.