Calculate your body mass index (BMI) from your height and weight in US or metric units, see your BMI category and the healthy weight range for your height.
What is BMI?
Body mass index (BMI) is a quick screening number that relates weight to height. Doctors and public health agencies use it to flag possible weight-related health risks in adults.
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25 to 29.9 | Overweight |
| 30 and above | Obesity |
These are the standard adult categories used by the CDC and WHO. Children and teens use age- and sex-specific percentiles instead.
Worked example
A person who is 5 ft 9 in (69 inches) and weighs 170 lb has a BMI of 703 × 170 ÷ 69² = 25.1, just inside the overweight category. The healthy weight range for that height is about 125 to 169 lb.
The limits of BMI
- Muscle: athletes with a lot of muscle can have a high BMI without excess fat.
- Fat distribution: BMI does not show where fat is stored. Waist size adds useful information.
- Age, sex and ethnicity affect body composition at the same BMI.
For a fuller picture, try the body fat calculator, and discuss your results with a healthcare professional.
Frequently asked questions
Is BMI accurate?
It is a reasonable screening tool for groups of people but can misclassify individuals, especially very muscular people and older adults.
What is BMI prime?
Your BMI divided by 25, the upper limit of the healthy range. A value of 1.0 or less means you are within or below it.
Related tools
BMI is a general screening measure for adults, not a diagnosis. It does not account for muscle, body shape, age, sex or ethnicity. Talk to a healthcare professional about your health.