How to calculate your BMI
Enter your height and weight to get your body mass index instantly. Your height and weight are never stored or sent anywhere. How ads and cookies work.
--
Enter your details to see your result
For adults 20 and older. Children and teens need age and sex based percentile charts.
The BMI formula
Body mass index compares your weight to your height. There are two versions of the same calculation, depending on your units.
Metric (kilograms and meters)
US units (pounds and inches)
Worked example
Someone who weighs 150 lb and is 5 ft 6 in (66 inches) tall: 66 × 66 = 4,356. Then 150 ÷ 4,356 = 0.03443, and 0.03443 × 703 = 24.2. That falls in the healthy weight range.
In metric, 68 kg at 1.68 m: 1.68 × 1.68 = 2.822. Then 68 ÷ 2.822 = 24.1.
Adult BMI chart
These are the standard adult categories used by the World Health Organization and the CDC.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity, class 1 |
| 35.0 to 39.9 | Obesity, class 2 |
| 40.0 and above | Obesity, class 3 |
What BMI can and cannot tell you
BMI is a fast screening number, not a diagnosis. It cannot tell muscle from fat, so a muscular athlete can land in the overweight range. It also ignores where fat is stored, and it can read differently for older adults, for different ethnic groups, and during pregnancy. If your result worries you, or you feel fine but your number is outside the healthy range, a doctor can look at waist size, blood pressure, and blood tests for a fuller picture.
BMI guides for specific situations
The adult chart above does not fit everyone. These guides cover the most common exceptions.
Common questions
How do you calculate BMI?
Divide weight in kilograms by height in meters squared. In pounds and inches, divide weight by height squared and multiply by 703.
What is a healthy BMI?
For adults, 18.5 to 24.9 is considered the healthy weight range.
Is the BMI calculation the same for men and women?
Yes. The formula is identical for adults of any sex, though body composition differs on average.
Can I use BMI for my child?
Not with this chart. For ages 2 to 19, BMI is compared with percentiles for the child's age and sex. Ask your pediatrician or use the CDC growth charts.
Is my information saved?
Your height and weight are not saved. The calculation runs in your browser and those numbers are never uploaded. Like most free sites, this one shows ads from Google, which may use cookies. See the privacy policy for details and opt-out choices.