How BMI is calculated

BMI = weight (kg) ÷ height (m)². For imperial units we use BMI = 703 × weight (lb) ÷ height (in)². The result is interpreted with the WHO categories:

Under 18.5 — Underweight
18.5 – 24.9 — Normal weight
25 – 29.9 — Overweight
30 + — Obese

BMI is a screening tool, not a diagnostic. It does not distinguish between muscle and fat. For athletes, pregnant people and the elderly, talk to a healthcare professional.

Frequently Asked Questions

Is the BMI Calculator free to use?

Yes, the BMI Calculator is 100% free to use. There are no subscriptions, no sign-ups, and no hidden fees.

Is my data safe when using the BMI Calculator?

Absolutely. All calculations performed by the BMI Calculator happen locally in your web browser. We do not store, track, or transmit your inputs or results to any server.

How accurate is the BMI Calculator?

Our BMI Calculator uses industry-standard formulas and methodology. You can view the exact formula and calculation logic used in the methodology section above to verify the math yourself.

Can I use the BMI Calculator on my mobile phone?

Yes! The BMI Calculator is fully responsive and works seamlessly on all devices including smartphones, tablets, and desktop computers.