BMI Calculator
BMI is a reference. Consult a healthcare professional.
- Choose the system: metric, with kilograms and centimetres, or imperial, with pounds and inches.
- Enter weight and height.
- The result shows your BMI, the matching range, and the weight interval considered healthy for your height.
BMI divides weight in kilograms by the square of height in metres. Someone at 70 kg and 1.75 m has a BMI of 22.9.
The World Health Organization ranges: below 18.5 is underweight; 18.5 to 24.9 is healthy; 25 to 29.9 is overweight; 30 and above is obesity, split into three classes.
The healthy weight interval shown is whatever keeps BMI between 18.5 and 24.9 for the height you entered.
BMI cannot tell muscle from fat. A heavily muscled athlete can register as overweight with no excess body fat at all.
It also ignores where fat sits, and abdominal fat correlates more strongly with cardiovascular risk than total weight. That is why waist circumference is usually measured alongside it.
Older adults, pregnant people, children and adolescents need their own references — for the last two groups, age-based percentile curves are used rather than fixed adult cut-offs.
BMI is a cheap, fast population screening tool, not a diagnosis. Individual interpretation belongs with a health professional.
Frequently asked questions
Not necessarily. The calculation uses only weight and height, so muscle counts the same as fat. People who train with weights regularly often have a raised BMI with no excess fat.
Not with these ranges. Children and adolescents are assessed with percentile curves specific to age and sex, because body composition changes throughout growth.
Not during pregnancy. Expected weight gain has its own reference, tracked through prenatal care.
Waist circumference is the most common, because fat around the abdomen is more strongly associated with cardiovascular risk than total weight.
No. The calculation runs in your browser and nothing is logged.