BMI Calculator
Enter your height and weight to see your body mass index, your category and the healthy weight range for your height. Works for children and teens aged 2–19 too.
How to use the BMI calculator
- Pick Metric or US units at the top.
- Enter your age and choose your sex. For ages 2 to 19, a months field appears for a more precise result.
- Enter your height and weight. Your BMI, category and place on the color scale appear instantly.
- The cards show the healthy weight range for your height and how far you are from it.
- Use the table on the side to see healthy weight ranges for other heights.
What is BMI?
Body mass index (BMI) is a simple measure of whether your weight suits your height. The World Health Organization (WHO) and doctors use it as a first screening step for underweight and overweight. It is easy to work out: divide your weight by the square of your height.
BMI = weight (kg) ÷ height² (m)
US units: BMI = 703 × weight (lb) ÷ height² (in)
For example, someone 5 ft 9 in (69 in) tall who weighs 180 lb has a BMI of 703 × 180 ÷ 69² = 26.6, which is overweight. Try it in the calculator.
BMI categories for adults
According to the WHO, a BMI under 18.5 is underweight, 18.5 to 24.9 is healthy, 25 to 29.9 is overweight and 30 or more is obese. Obesity is split into three classes: 30–34.9, 35–39.9 and 40 or more. To turn the healthy range into pounds or kilograms, multiply 18.5 and 24.9 by your height squared.
A person 180 cm (5 ft 11 in) tall weighing 90 kg (198 lb) has a BMI of 27.8. The healthy range for that height is 59.9–80.7 kg, so they would need to lose about 9.3 kg (20.6 lb) to reach the top of it. Open this example.
BMI for children and teens
Between ages 2 and 19, body shape changes quickly, so adult cut-offs do not apply. A child’s BMI is compared with other children of the same age and sex and given as a percentile. This calculator uses the CDC growth charts, month by month.
| Percentile | Category |
|---|---|
| Below 5th | Underweight |
| 5th to 84th | Healthy weight |
| 85th to 94th | Overweight |
| 95th or above | Obese |
For example, a girl aged 12 years and 6 months who is 152 cm (5 ft) tall and weighs 45 kg (99 lb) has a BMI of 19.5. That is the 63rd percentile, in the healthy range. Open this example.
Limits of BMI
BMI cannot tell muscle from fat. It can run high for athletes and muscular people, and look better than it is for older adults who have lost muscle. It is not used during pregnancy and does not show where fat is stored. For a closer look, try the body fat calculator, or the ideal weight calculator for a target weight for your height. Everything runs in your browser and nothing you enter is sent to a server.
Frequently asked questions
What is a healthy BMI?
For adults, a healthy BMI is 18.5 to 24.9. A BMI of 25 to 29.9 is overweight, 30 or more is obese, and under 18.5 is underweight. Children have no fixed number; their BMI is compared with others of the same age and sex as a percentile.
How do I calculate BMI?
Divide your weight in kilograms by your height in meters squared. For 165 cm and 60 kg: 60 ÷ (1.65 × 1.65) = 22.0. With pounds and inches, use 703 × weight ÷ height².
Is BMI different for men and women?
Not for adults: the same cut-offs apply to everyone. Women usually carry more body fat at the same BMI, but the categories do not change. For ages 2 to 19, boys and girls have separate growth charts, so sex matters.
Is BMI accurate if I am muscular?
BMI cannot tell muscle from fat, so athletes and muscular people may be labeled overweight. In that case, body fat percentage or waist size gives a better picture.
Is my data saved?
No. Everything is calculated in your browser and nothing is sent anywhere. Your last values are remembered only on your own device for convenience; press Clear to remove them.