BMI Calculator

Body mass index is weight in kilograms divided by height in metres squared. It was devised in the nineteenth century as a way of describing populations, not individuals, and that origin explains both why it is still used and why it is so often misleading about any particular person.

What it does well is give a quick, cheap screening figure across a large group. What it cannot do is distinguish muscle from fat, account for frame size, or adjust for age or sex. A well-trained athlete routinely reads as overweight or obese on it while carrying very little body fat, and someone with little muscle can sit comfortably in the healthy band while carrying too much.

There is also a population caveat worth knowing. Several health bodies apply lower thresholds for people of South Asian, Chinese and other Asian descent, because the health risks associated with a given BMI appear at a lower number. The standard bands shown here are the general international ones.

The calculator accepts metric or imperial input and shows which band the result falls in, along with the weight range that would place your height in the healthy band — which is usually the more actionable figure.

Nothing you enter is transmitted. Height and weight are personal, and there is no reason for a website to receive them.