UK BMI Calculator — Body Mass Index (NHS)

The NHS BMI formula is: BMI = weight (kg) ÷ height (m)². Take your weight in kilograms and divide it by your height in metres, squared. For example: 75kg ÷ (1.75 × 1.75) = 24.5. That is in the healthy range. This calculator does the maths for you. Just enter your height and weight.

The NHS BMI scale has four categories. Under 18.5 is underweight. Between 18.5 and 24.9 is a healthy weight. Between 25 and 29.9 is overweight. 30 or above is obese. If you are of South Asian or Chinese background, the thresholds are lower. Overweight starts at 23, and obese at 27.5.

Divide your weight in kilograms by your height in metres squared. So if you weigh 70kg and are 1.75m tall: 70 ÷ (1.75 × 1.75) = 22.9. Your estimated BMI is 22.9, which is in the healthy range. You do not need to do this by hand. Just enter your height and weight above and your estimated BMI appears straight away.

The NHS says a healthy BMI is between 18.5 and 24.9. Below 18.5 is underweight. Between 25 and 29.9 is overweight. 30 and above is obese. If you are of South Asian or Chinese background, your healthy range is slightly lower. Talk to your GP if you are unsure what your result means for you.

Yes. The NHS uses the same BMI scale for women and men. The healthy range is 18.5 to 24.9 for both. Women naturally carry a little more body fat than men at the same BMI, but the NHS does not use different cut-offs by sex. This calculator works for all adults aged 18 and over.

BMI does not measure body fat directly. It only looks at your height and weight. This means it can be misleading for some people. Muscular people often get a high BMI even though they have low body fat. Older adults may have a normal BMI but still carry too much fat. BMI is a useful guide, but it is not the full picture. Your GP can give you a more complete assessment.

Your ideal weight is whatever keeps your BMI between 18.5 and 24.9. For someone who is 5'8" (173cm), that is roughly 55 to 79kg. For someone who is 5'4" (163cm), it is roughly 49 to 70kg. Enter your height above and the calculator will show your personal healthy weight range.

No. This calculator is for adults aged 18 and over. For children, healthy BMI ranges change with age and sex, so the adult scale does not apply. The NHS has a separate child BMI tool at nhs.uk. Use that instead for anyone under 18.

A BMI in the overweight or obese range raises your risk of type 2 diabetes, heart disease, high blood pressure, some cancers, and joint pain. The higher your BMI, the greater the risk. Losing even 5 to 10 percent of your body weight can make a real difference. Talk to your GP if your result is in the overweight or obese range.

If you are of South Asian, Chinese, or other Asian background, your health risks are higher at a lower BMI. The NHS recommends different thresholds for these groups. Overweight starts at BMI 23, not 25. Obese starts at BMI 27.5, not 30. If this applies to you, use these lower cut-offs and speak to your GP about your result.