Body mass index compares your weight with your height. It is a quick screening number used by doctors and health programmes, but it has limits, and it is best read together with other information.
The formula
BMI equals weight in kilograms divided by height in metres squared. A person of 70 kg and 170 cm has a BMI of 70 / (1.7 x 1.7) = 24.2.
Categories for adults
- Below 18.5: underweight.
- 18.5 to 24.9: normal weight.
- 25 to 29.9: overweight.
- 30 and above: obese.
How to use the calculator
- Choose metric or imperial units.
- Enter your weight and height.
- Read your BMI, category and the weight range that counts as normal for your height.
What BMI cannot tell you
BMI does not separate muscle from fat, so a very muscular person may show a high number. It also does not consider age, sex or where the fat is stored. Children, teenagers, older adults and pregnant women need different charts. Use BMI as a starting point and talk to a doctor for advice.
Frequently asked questions
Is BMI a diagnosis?
No. It is a screening number, not a diagnosis.
Do Asian populations use different limits?
Some health bodies suggest lower cut-offs for Asian adults. Ask your doctor which guideline applies to you.
Is my data stored?
No. It stays in your browser.
Ready to start?
Open BMI Calculator