BMI Calculator (Body Mass Index)

How to read your BMI result

BMI divides your weight in kilograms by the square of your height in metres. The World Health Organization groups adult results into bands: below 18.5 is underweight, 18.5 to 24.9 is the healthy range, 25 to 29.9 is overweight and 30 or more is obese. BMI Prime is simply your BMI divided by 25, so a BMI Prime above 1.0 means you are above the upper limit of the healthy range.

Because the formula only uses height and weight, it cannot tell muscle from fat. A sprinter or weightlifter with a lot of lean mass can show an "overweight" BMI while having low body fat, and an older adult who has lost muscle can show a "normal" BMI while carrying more fat than is healthy. Treat BMI as a quick screening number, not a diagnosis.

Second example: a shorter adult

Someone 160 cm tall weighing 68 kg has a height of 1.60 m. Squaring it gives 2.56 m². Dividing 68 by 2.56 gives a BMI of 26.6, which falls in the overweight band. To reach a BMI of 24.9 at the same height they would weigh 24.9 × 2.56 = 63.7 kg, so the healthy-range ceiling is about 4.3 kg lower than their current weight.

Asian and other population cut-offs

Research summarised by the WHO found that many Asian populations have higher health risk at lower BMI values. For that reason Indian guidelines often treat 23 to 24.9 as overweight and 25 or more as obese. If you are of South Asian origin, compare your result with both sets of cut-offs and discuss it with a doctor. BMI is also not designed for children or pregnant women; children use age- and sex-specific percentiles instead.