BMI calculator for adults

How BMI is calculated

BMI is your weight in kilograms divided by the square of your height in metres. WHO gives this example: 70 kg at 1.75 m is 70 ÷ (1.75 × 1.75) = 22.9. For feet and inches, the calculator converts exactly, using 1 inch = 2.54 cm and 1 pound = 0.45359237 kg. So 5 feet 7 inches and 150 pounds gives a BMI of 23.5. The BMI is shown to one decimal, and the category is read from that number.

Two scales: WHO and Asian Indian

The WHO table for adults over 20 is: below 18.5 underweight, 18.5 to 24.9 normal weight, 25.0 to 29.9 pre-obesity, 30.0 to 34.9 obesity class I, 35.0 to 39.9 obesity class II, and 40 or more obesity class III.

A WHO expert consultation in 2004 found that many Asian people have a higher risk of type 2 diabetes and heart disease at BMIs below 25. It kept the WHO cut-offs as the international standard and suggested extra action points for countries to use. In India, a 2009 consensus statement by Indian experts recommends these cut-offs for Asian Indians: normal 18.0 to 22.9, overweight 23.0 to 24.9, and obesity 25 or more.

Worked example: 165 cm and 68 kg gives a BMI of 25.0. That is pre-obesity on the WHO scale but obesity on the Indian scale, which is why both are shown.

Not medical advice

BMI is a quick screening measure, not a full health check. It does not measure body fat directly or tell muscle from fat. Talk to a doctor about your health. This calculator is for adults only; for children and teenagers, age and sex must be taken into account, so ask a doctor to use growth charts.