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BMI Calculator

Work out your body mass index (BMI) from height and weight, in metric or imperial units, and see its WHO adult category. A screening measure for adults, not a diagnosis.

Units Metric (metres and kilograms) Imperial (inches and pounds)

Height (m) Weight (kg)

Enter a height and a weight.

Body mass index (BMI)-

WHO adult category-

BMI is a screening measure for adults. It is not a diagnosis, and it does not measure body fat, muscle, bone, age or sex. Children and teenagers need BMI-for-age charts instead. Everything runs in your browser; no height, weight or result is sent or stored.

How it works

Formula. Metric: BMI = weight in kilograms ÷ (height in metres × height in metres). Imperial: BMI = 703 × weight in pounds ÷ (height in inches × height in inches). The calculation uses exact fractions. The result is shown to one decimal place, rounded half up (0.05 rounds up to 0.1).

Categories. The World Health Organization's cut-offs for adults are:

under 18.5: underweight
18.5 to under 25: normal weight
25 to under 30: overweight
30 and over: obese

Source: World Health Organization, "Obesity and overweight" fact sheet, and its adult BMI classification. The category is decided from the exact BMI before rounding, so a BMI of 18.49 is underweight even though it is shown as 18.5.

Limits. Use BMI for adults only. It does not account for muscle mass, bone, age, sex or body shape, so a high BMI can reflect muscle rather than fat. Children and teenagers need BMI-for-age charts. Accepted inputs: height 0.5 to 2.5 m or 20 to 100 in; weight 1 to 700 kg or 2 to 1500 lb.