BMI Calculator — Free, Metric & Imperial
Calculate your Body Mass Index from weight and height, in metric or imperial. 100% in your browser — free, no sign-up.
- ✓Free
- ✓No sign-up
- ✓Runs in your browser — files never uploaded
- ✓No watermark
How to
- 1Pick metric or imperial units.
- 2Enter your weight and height.
- 3Read your BMI and category.
What is BMI?
Body Mass Index (BMI) is a number calculated from your weight and height that gives a general indication of whether you are underweight, a normal weight, overweight, or obese. It is a quick screening guide used widely in health contexts.
How it works
Enter your weight and height in metric (kg, cm) or imperial (lb, in). BMI is computed in your browser using the standard formula and matched to the standard category ranges. Nothing is sent anywhere.
The formula
BMI = weight (kg) ÷ height (m)². In imperial units, BMI = 703 × weight (lb) ÷ height (in)². For example, 70 kg at 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. The category cut-offs follow the World Health Organization (WHO) classification for adults.
BMI categories
The usual ranges are: under 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, and 30 or above obese. They apply to adults and are a general guide, not a personal diagnosis.
Limits of BMI
BMI does not distinguish muscle from fat or account for age, sex, or body composition, so very muscular people can read as overweight. Treat it as a starting point and consult a professional for a real assessment.
FAQ
Which units can I use?+
Both metric (kg, cm) and imperial (lb, in). Switch units and the formula adjusts automatically.
What are the BMI categories?+
Under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obese. These apply to adults as a general guide.
Is BMI accurate for everyone?+
No. BMI does not separate muscle from fat or account for age, sex, or build, so it is a screening guide, not a diagnosis.
Is my data private?+
Yes. BMI is calculated in your browser; nothing is sent anywhere.
Is it free?+
Yes, completely free — no sign-up and no watermark.
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