BMI Calculator
Enter your height and weight to work out your Body Mass Index. Everything updates live and stays on your device.
Free online BMI calculator
Body Mass Index (BMI) is a quick way to estimate whether your weight is in a healthy range for your height. This calculator works in both metric and imperial units and updates the moment you type. Switch between kilograms and centimetres or pounds and inches, and the result and category are recalculated instantly against the standard World Health Organization ranges: underweight below 18.5, normal from 18.5 to 24.9, overweight from 25 to 29.9 and obese at 30 and above.
Your data stays private
All calculations happen directly in your browser — your height and weight are never sent to a server or stored anywhere. This tool is provided for general information only and is not medical advice; BMI does not account for muscle mass, body composition, age or other factors, so speak to a healthcare professional about what your results mean for you.
Frequently asked questions
How is BMI calculated?
In metric units, BMI is your weight in kilograms divided by the square of your height in metres. In imperial units, it is 703 times your weight in pounds divided by the square of your height in inches. Both formulas give the same number.
Is BMI a diagnosis?
No. BMI is a screening estimate, not a medical diagnosis, and this tool is informational rather than medical advice. It does not measure body fat directly or account for muscle, so always consult a healthcare professional for guidance.