Body mass index (BMI) relates your weight to your height to place you in a category. It's a quick, useful reference — but it doesn't tell the whole story.
The formula
BMI = weight (kg) ÷ height² (m). A person of 70 kg and 1.75 m has a BMI of 70 ÷ 3.0625 = 22.9.
The categories
- Under 18.5 — underweight
- 18.5–24.9 — normal weight
- 25.0–29.9 — overweight
- 30.0 and above — obesity
What it doesn't measure
BMI is a population estimate. It doesn't distinguish muscle from fat, so a very muscular person can read as "overweight" without excess fat. It also doesn't apply the same way to children, pregnant people or older adults.
See your number and healthy range with the BMI Calculator.
Related tools