BMI calculator
Body mass index (BMI) is your weight in kilograms divided by the square of your height in metres. Enter yours to see which World Health Organization band it falls in. The calculator is for adults.
- Underweight< 18.5
- Healthy weight18.5–24.9
- Overweight25.0–29.9
- Obesity class 130.0–34.9
- Obesity class 235.0–39.9
- Obesity class 3≥ 40.0
Example: 90 kg, 175 cm
90 ÷ (1.75 × 1.75) = 29.4
Population categories, not a diagnosis. No band on its own means treatment is or is not appropriate.
Source: World Health Organization, adult BMI classification
BMI chart: weight by height
For each height, the chart shows the weights at which BMI falls in the WHO healthy weight, overweight and obesity bands. The adult bands are the same for women and men.
| Height | Healthy weight (kg) | Overweight (kg) | Obesity (kg) |
|---|---|---|---|
| 150 cm | 42–56 | 57–67 | 68+ |
| 155 cm | 45–60 | 61–72 | 73+ |
| 160 cm | 48–63 | 64–76 | 77+ |
| 165 cm | 51–68 | 69–81 | 82+ |
| 170 cm | 54–72 | 73–86 | 87+ |
| 175 cm | 57–76 | 77–91 | 92+ |
| 180 cm | 60–80 | 81–97 | 98+ |
| 185 cm | 64–85 | 86–102 | 103+ |
| 190 cm | 67–90 | 91–108 | 109+ |
| 195 cm | 71–95 | 96–114 | 115+ |
| 200 cm | 74–99 | 100–119 | 120+ |
Worked out from the BMI formula and rounded to whole kilograms. The chart has the same limits as BMI itself: it cannot tell muscle from fat.
Waist size
Fat around the waist is more closely linked to risk than weight alone.
Blood pressure
One of the first measurements in judging risk.
Blood tests
Sugar, blood fats and whatever else the doctor asks for.
Medical history
Conditions, medicines and what you have already tried.
How BMI is calculated
BMI = weight (kg) ÷ height (m)². Someone 175 cm tall weighing 90 kg has a BMI of 90 ÷ (1.75 × 1.75), about 29.4.
It is a ratio, not a measurement of fat. That is why it is quick and cheap, and why it has limits.
What BMI will not tell you
It cannot tell muscle from fat: an athlete with a lot of muscle can have a BMI in the overweight band. It does not say where fat is carried, and fat around the waist is more closely linked to heart disease and diabetes than weight alone. It is not meant for children, pregnant women, or older people who have lost muscle.
That is why a doctor usually looks at waist size, blood pressure, blood tests and your medical history as well.
Waist size as a second number
The WHO describes increased health risk at a waist above 94 cm for men and 80 cm for women, and substantially increased risk above 102 cm for men and 88 cm for women. Measure halfway between the lowest rib and the top of the hip bone, after a normal breath out.
When it is worth talking to a doctor
If your weight worries you, if you have tried to lose weight and could not keep it off, or if you have high blood pressure, diabetes or other problems linked to weight, it is sensible to talk it through with a doctor, whatever band your number falls in. A doctor looks at the whole picture and tells you what your options are, including that you may not need any treatment at all.
- What is a normal BMI?
- For adults, the WHO puts a healthy BMI at 18.5 to 24.9. From 25 the WHO calls it overweight, and from 30 obesity. These are population bands: what your number means for you is a question for a doctor rather than a table.
- What BMI counts as obesity?
- The WHO puts obesity at a BMI of 30 or more: 30 to 34.9 is class 1, 35 to 39.9 class 2, and 40 or more class 3.
- Is BMI the same for women and men?
- Yes, the WHO adult bands are the same for women and men. Waist size is where they differ: the WHO gives increased health risk above 80 cm for women and above 94 cm for men.
- Does this BMI calculator work for children?
- No. For children and teenagers BMI is read against growth charts for their age and sex. This calculator is for adults.
- Does my BMI decide whether I get treatment?
- Not on its own. BMI is one of the things a doctor looks at. Whether any treatment is right for you is decided by a doctor after a consultation, from your history, measurements and tests.
- Do you store my numbers?
- No. The calculation happens in your browser and your height and weight are not sent anywhere.
Want to talk to a doctor about your weight?
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