BMI Calculator
Calculate your Body Mass Index with metric or imperial units
Calculates Body Mass Index from your height and weight, in either metric (cm/kg) or imperial (ft/in/lb) units, and shows which standard BMI category the result falls into.
How it works
Metric BMI is weight in kilograms divided by height in meters squared; imperial BMI uses the equivalent formula scaled for pounds and inches. The result is checked against the standard adult BMI ranges — under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese — and updates instantly as you type.
Frequently asked questions
Is BMI an accurate measure of health?
BMI is a simple screening number based only on height and weight — it doesn't account for muscle mass, body composition, age, or sex, so it can be misleading for athletes or anyone with an atypical build. It's a starting point, not a diagnosis.
What BMI ranges does it use?
The standard adult categories: under 18.5 is underweight, 18.5 to 24.9 is normal, 25 to 29.9 is overweight, and 30 or above is obese. These are general population ranges, not personalized medical thresholds.
Can I switch between metric and imperial units?
Yes — use the toggle at the top to switch between centimeters/kilograms and feet-inches/pounds; your result recalculates as soon as you have valid numbers in the fields for whichever system is selected.
What happens if I enter 0 or a negative number?
You'll get an inline error instead of a result — height and weight both have to be positive numbers for the calculation to make sense.
Is my height and weight data stored or sent anywhere?
No — the calculation happens entirely in your browser. Nothing you enter is uploaded or saved anywhere once you leave the page.