Work out your body mass index from your height and weight, and see the category it falls in. Free, in metric or imperial units.
Body mass index puts weight and height on one scale, so two people of different heights can be compared with one number. It is a screening measure, and it describes a ratio, not a body.
The calculation is one division:
BMI = weight in kilograms / (height in meters)^2
Imperial entries are converted first. Height is divided by 39.37007874 to reach meters, and weight by 2.2046226218 to reach kilograms. Changing the unit selector converts what you already typed, so 175 cm and 70 kg become 68.8976 in and 154.3236 lb, and both give the same index.
The category is decided by the index alone. The calculator prints Underweight below 18.5, Healthy weight from 18.5 up to 25, Overweight from 25 up to 30, Class 1 obesity from 30 up to 35, Class 2 obesity from 35 up to 40, and Class 3 obesity at 40 and above. The result states that these are the adult WHO and CDC categories.
Height must be between 50 and 275 cm, and weight between 15 and 500 kg.
The index is 22.9, and the category is Healthy weight.
Height is squared, so it moves the result a long way. The same 70 kg at 160 cm gives 27.3 and reads Overweight. At 190 cm it gives 19.4 and reads Healthy weight. One weight covers three categories.
Height is one number in inches, so 5 feet 9 inches is 69. With 185 lb the index is 27.3, and the category is Overweight.
The calculator prints Healthy weight from 18.5 up to 25. Below that it prints Underweight, and above it Overweight and then the three obesity classes. These labels are bands drawn across a population. The tool prints the band your index falls in and nothing more. It sets no target.
The index is shown to one decimal place, and the category is decided on the unrounded value. At 175 cm and 56.6 kg the exact index is just under 18.5, so the display rounds up while the category stays Underweight. The same happens at the top of the band, where 175 cm and 76.5 kg shows 25.0 and reads Healthy weight.
No. Height and weight are the only two numbers it uses. It cannot separate muscle from fat, it does not know where weight sits on the body, and it knows nothing about your health. A trained athlete and a person carrying more fat can share an index. Ask a doctor what your own number means.
No. The categories in this tool are the adult ones, and the result says so. A growing child is read against a chart for age and sex, which this tool does not hold.
Height is one number, so convert first and multiply the feet by 12. The Length Converter handles feet and inches, and the Weight Converter handles stones and pounds.
No. There is no account and no server call. Nothing you type leaves the browser, nothing is saved, and every field returns to its default when you reload the page. The tool also works with no internet connection after your first visit.
The ratio is older than the name. Adolphe Quetelet described it in the 1830s as a way to summarize a population, and it was called the body mass index much later, in 1972. Both uses were statistical, which is much of why one index says so little about one person.
The index carries units, kilograms per square meter, although it is almost never written with them. An index of 22.9 is 22.9 kg/m^2.
For the energy side of the same two measurements, use the BMR Calculator and the TDEE Calculator.