What's your BMI?
Body mass index compares your weight with your height. Enter both and you'll get your BMI, the range it sits in, and what it can and can't tell you.
How BMI is worked out
BMI is your weight in kilograms divided by your height in metres, squared. A person who is 1.75 m tall and weighs 75 kg has a BMI of 75 ÷ (1.75 × 1.75) = 24.5. The calculator converts pounds, feet and inches for you.
What the ranges mean
The World Health Organization uses the same adult ranges everywhere: under 18.5, 18.5 to 24.9, 25 to 29.9, and 30 or more. They were set from large population studies, so they describe groups well and individuals less well.
Where BMI falls short
BMI only knows your height and weight. It can't see how much of that weight is muscle, so trained people often land in a higher range than their body shape suggests. It also doesn't show where fat sits, which matters more than the total. Waist size and body-fat estimates add what BMI leaves out.
These ranges are for adults. Children and teenagers are measured against growth charts instead.
Frequently asked questions
- Is BMI different for men and women?
- The formula and the adult ranges are the same. Men and women of the same BMI usually carry different amounts of body fat, which is one reason BMI is only a rough guide.
- Does muscle affect BMI?
- Yes. Muscle is dense, so building it raises your weight and your BMI even as your body fat falls.
- What's a better measure than BMI?
- None is perfect at home, but a body-fat estimate from tape measurements, plus your waist size, tells you more than BMI alone.
A project of Health Is Power Foundation — a registered public-benefit nonprofit.