Health / 01
BMI Calculator
Work out your body mass index from your height and weight, in metric or US units, with the WHO category, the healthy weight range for your height, and the lower action points used for Asian populations.
BMI Calculator: BMI is your weight in kilograms divided by the square of your height in metres. The page shows it to one decimal, places it in the World Health Organization's adult categories, and works out the weights that give a BMI of 18.5 to 24.9 at your height. It also shows where you sit on the public health action points a WHO expert consultation proposed for Asian populations, where health risks rise at a lower BMI. Runs 100% locally in your browser with zero server file uploads.
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- Health & sport tools
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- In your browser
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- Free · no sign-up
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- Ready to use
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Your BMI
kg/m²24.1 Healthy weight
BMI is a screening number for adults, not a diagnosis. It cannot tell muscle from fat, so it overstates fat in athletes, and it does not apply during pregnancy or to children and teenagers, who are assessed with growth charts by age and sex. A doctor can tell you what your weight means for your health.
Where the numbers come from
BMI is weight in kilograms divided by height in metres squared; in US units the same result is weight in pounds divided by height in inches squared, times 703. A person 1.75 m tall weighing 70 kg has a BMI of 70 ÷ 1.75², which is 22.9. The categories are the World Health Organization's for adults, set out in its fact sheet on obesity and overweight.
The Asian action points of 23 and 27.5 come from a WHO expert consultation published in The Lancet in 2004 (volume 363, pages 157–163), which found that the proportion of Asian people at high risk of type 2 diabetes and heart disease is substantial below the usual cut-off of 25. The consultation left each country to choose its own cut-offs, so a national guideline may use slightly different numbers.
Reading your result
The number is shown to one decimal and the category is read from that same figure, so a BMI shown as 25.0 is always labelled overweight. Near a boundary, a small change in weight or a measurement taken in shoes moves the category, which is one reason a single reading matters less than the trend. For a steady picture, weigh yourself at the same time of day and measure your height without shoes.
How to use it
- Choose metric or US units.
- Enter your height and weight.
- Read your BMI, its category, and the healthy weight range for your height.
Privacy & limitations
Everything is calculated in your browser. Your height and weight are never sent anywhere or stored; only your choice of units is remembered.
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Frequently asked questions
What are the BMI categories?
For adults, the WHO classes a BMI below 18.5 as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight, and 30 or more as obesity, in three classes starting at 30, 35, and 40.
Why are there different cut-offs for Asian people?
People of Asian descent tend to have more body fat, and a higher risk of type 2 diabetes and heart disease, at the same BMI. A WHO expert consultation in 2004 proposed action points of 23 for increased risk and 27.5 for high risk, and several countries use lower cut-offs of their own.
Is BMI accurate?
It is a quick screening number, not a measure of body fat. It overstates fat in muscular people, understates it in people who have lost muscle, and says nothing about where fat is carried. Waist size and a doctor's assessment add what BMI leaves out.
Can I use it for a child or during pregnancy?
No. Children and teenagers are assessed with BMI-for-age growth charts, which compare them with others of the same age and sex, and weight gain in pregnancy is tracked differently. Ask a doctor, midwife, or health visitor.
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