BMI Calculator

For adults, 18.5 to 24.9. Below 18.5 counts as underweight, 25 to 29.9 as overweight, and 30 or above as obese. These bands come from the World Health Organization and are the same ones your GP uses. For some family backgrounds NICE lowers those cut-offs, covered below.

As a quick screen, useful. As a personal verdict, limited. BMI can't tell muscle from fat, so muscular people often score above range while being perfectly healthy, and it says nothing about where fat sits. It also isn't used during pregnancy. The NHS suggests measuring your waist alongside it for a fuller picture, and watching how your weight trends over time.

Waist to height is a strong partner to it. NICE and the NHS advise keeping your waist to less than half your height, because fat around the middle carries the most risk. A tape measure plus your BMI tells you far more than either number alone.

No, the adult formula and the bands are the same for everyone. That simplicity is part of why it's used everywhere, and also one of its known limits, since men and women carry muscle and fat differently.

The calculation is the same for everyone, but the risk thresholds aren't. The NHS and NICE use lower cut offs, 23 for overweight and 27.5 for obese, for adults with an Asian, Black African, African Caribbean or Middle Eastern background, including mixed backgrounds, because health risks rise at lower BMIs in these groups. Pick your background in the calculator and every number on the page adjusts, the same way the NHS calculator does.

A weight that puts your BMI between 18.5 and 24.9. Type your height into the calculator above and it shows the exact range for you, in your units.

The calculation is the same for all adults, so this calculator is for people 18 and over. Children and teenagers use age-adjusted percentile charts instead. For over 65s BMI can be less reliable, because muscle naturally falls with age, so treat it as a rough guide there and lean on your GP's advice.

See a GP if you're below the healthy range, because difficulty gaining weight or unexplained weight loss can have an underlying cause. If you're in the obese band and want support, your GP can refer you to NHS weight management services. And whatever your number, if you're worried about your weight, eating or health, a GP is never the wrong call.

It uses the exact thresholds the WHO and NICE publish and the NHS applies, including the lower cut offs for higher risk ethnic backgrounds, and the working is shown on this page so you can check it against any source. The category always matches the number on screen, nothing you type is saved, and there are no ads. When the guidance changes, this page changes with it.

Since your height is fixed, BMI only moves with weight, and weight moves with a steady calorie deficit. Our free TDEE calculator works out how many calories you burn a day and the target that loses about half a kilo a week.