About bmi calculator
Body Mass Index compares your weight with your height. It is a quick screening number, not a diagnosis.
Formula
BMI = weight in kg ÷ (height in metres)². Someone who weighs 70 kg and is 1.70 m tall has a BMI of 70 ÷ 2.89 = 24.2.
Standard categories
- Below 18.5: underweight.
- 18.5 to 24.9: normal.
- 25 to 29.9: overweight.
- 30 and above: obese.
Limits
BMI does not distinguish muscle from fat, and the risk levels differ between populations. Several health bodies suggest lower cut-offs for people of South Asian origin, so ask your doctor how to read your number.
A worked example
A person weighing 70 kg at 1.70 m tall has a BMI of 70 ÷ 1.70² = 24.2, in the normal range. At 82 kg the same person would have a BMI of 28.4, in the overweight range. Waist size and body composition give extra context.
