BMI Calculator
Calculate your body mass index (BMI) from your height and weight, in metric or imperial units. BMI is your weight in kilograms divided by your height in metres squared, and it is placed in a weight range for adults.
Enter your height and weight in centimetres and kilograms, or in feet, inches and pounds. You get your BMI to one decimal place, the range it falls in and the weight range for your height that reads as normal weight. BMI is a general screening figure for adults, not a diagnosis.
BMI Calculator
Your BMI
Enter your height and weight to see your BMI.
What BMI is
Body mass index (BMI) compares your weight with your height in one number: your weight in kilograms divided by your height in metres squared. It is quick to work out, which is why it is used to screen adults for weight ranges that may need a closer look. It is a screening figure, not a diagnosis, and it says nothing on its own about whether you are healthy.
BMI ranges for adults
This calculator uses the WHO adult cut-offs of 18.5, 25 and 30. The range is chosen from your BMI as shown, rounded to one decimal place.
| Range | BMI |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 to 24.9 |
| Overweight | 25 to 29.9 |
| Obesity | 30 or more |
Worked examples
Each example was produced by entering the inputs shown into this calculator, so you can repeat it above and get the same figures.
Example 1: 170 cm and 70 kg
| Item | Result |
|---|---|
| Height | 170.0 cm |
| Weight | 70.0 kg |
| BMI | 24.2 |
| Range | Normal weight |
| Weight range for this height | 53.5 kg to 72.0 kg |
Example 2: 5 ft 7 in and 160 lb
| Item | Result |
|---|---|
| Height | 5 ft 7.0 in |
| Weight | 160.0 lb |
| BMI | 25.1 |
| Range | Overweight |
| Weight range for this height | 118.1 lb to 159.0 lb |
What BMI cannot tell you
- It does not measure body fat, and it cannot tell muscle from fat. Very muscular people can have a high BMI without extra fat.
- It does not show where fat is carried on the body.
- It is not for children and teenagers, whose BMI is read against growth charts for their age and sex.
- It can mislead for older adults and during pregnancy.
- Some health guidelines use different cut-offs for some groups, for example for South Asian adults. This calculator uses the general WHO adult ranges only and does not apply them.
For questions about your weight or health, ask a doctor or another health professional.
How this calculator works
Inputs
- Units
- Metric (centimetres and kilograms) or imperial (feet, inches and pounds).
- Height
- In centimetres from 100 to 250, or in whole feet plus inches (leave inches empty for 0).
- Weight
- In kilograms from 20 to 500, or in pounds.
Results
- BMI (kg/m²)
- Weight divided by height squared, shown to one decimal place.
- Weight range
- Underweight, normal weight, overweight or obesity, using the WHO adult cut-offs.
- Weight range for your height
- The weights at your height whose BMI reads 18.5 to 24.9, and how far your weight is above or below that range.
Formulas
Body mass index
BMI = weight in kg / (height in m x height in m)
Weight range for a height
Weight = BMI x (height in m x height in m), for BMI 18.5 and BMI 24.9
Worked example
A person 170 cm tall who weighs 70 kg has a BMI of 70 / (1.70 x 1.70) = 70 / 2.89 = 24.22, shown as 24.2, which is in the normal weight range. At 170 cm, BMI 18.5 to 24.9 is 53.5 kg to 72.0 kg.
Assumptions
- For adults only. The WHO cut-offs used here do not apply to children and teenagers, whose BMI is read against growth charts for their age and sex.
- The ranges are the WHO adult cut-offs: below 18.5 is underweight, 25 or more is overweight and 30 or more is obesity. The range from 18.5 up to 25 is called normal weight here.
- The BMI is shown to one decimal place, rounded half up, and the range is chosen from that shown figure, so a displayed 25.0 is never labelled normal weight.
- The weight range for your height is the weights whose BMI reads 18.5 to 24.9.
- Heights from 100 to 250 cm and weights from 20 to 500 kg are accepted. These limits catch typing slips; they are not medical limits.
- The same cut-offs are used for everyone. Some health guidelines use different cut-offs for some groups, for example for South Asian adults, and this calculator does not apply them.
- BMI does not measure body fat or muscle, and it does not show where fat is carried. It can mislead for athletes, very muscular people, older adults, and during pregnancy.
- This is a general calculation, not medical advice or a diagnosis. For questions about your weight or health, ask a doctor or another health professional.
- Your entries stay in your browser. They are not sent anywhere, saved, or put in the page address.
Common questions
- How do I calculate BMI?
- Divide your weight in kilograms by your height in metres squared. For 70 kg and 170 cm that is 70 divided by 1.7 times 1.7, which is about 24.2. In pounds and inches, the calculator first converts to kilograms and centimetres so the result is the same.
- What is a normal BMI?
- The WHO adult ranges call a BMI from 18.5 up to 25 normal weight. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obesity. These are general ranges for adults, and BMI alone does not say whether someone is healthy.
- Can I use this BMI calculator in pounds, feet and inches?
- Yes. Choose Imperial, then enter whole feet, inches and weight in pounds. The calculator converts them exactly and gives the same BMI as the metric entry for the same person.
- Is BMI accurate for everyone?
- No. BMI uses only height and weight, so it cannot tell muscle from fat or show where fat is carried. It can read high for very muscular people and miss low muscle in older adults. It is a quick screening figure, not a diagnosis.
- Does this calculator work for children?
- No. It is for adults. For children and teenagers, BMI is compared with growth charts for their age and sex, which this calculator does not use. Ask a doctor or school health service.
- Do South Asian adults use different BMI ranges?
- Some health guidelines use different cut-offs for some groups, including South Asian adults. This calculator uses the general WHO adult ranges only and does not apply them, so ask a doctor how to read your result.
- What is the weight range for my height?
- It is the weights at your height whose BMI reads from 18.5 to 24.9, which the calculator works out from your height and shows next to your own weight.
Sources
- Body mass index (BMI), Global Health Observatory – World Health Organization (checked )
- Obesity and overweight, fact sheet – World Health Organization (checked )