How to use the BMI Calculator
- Choose US or metric units.
- Enter your height and weight.
- Read your BMI, category and the healthy weight range for your height.
How it works
BMI = weight (kg) ÷ height (m)² = 703 × weight (lb) ÷ height (in)²Adult categories (WHO / CDC): under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 or more obesity.
Frequently asked questions
Is BMI accurate for athletes?
Not always. BMI does not distinguish muscle from fat, so very muscular people can be classified as overweight. Waist circumference and body-fat measurements add context.
Does BMI work for children?
No. Children and teens use BMI-for-age percentiles that compare them with others of the same age and sex.