How to Calculate BMI (Body Mass Index)

Body Mass Index (BMI) is a quick screening number doctors and fitness apps use to estimate whether your weight is in a healthy range for your height. It is not a diagnosis, but it is a useful, free starting point that only needs two numbers to compute.

The BMI formula

BMI is calculated as weight in kilograms divided by height in meters squared: BMI = kg / m². In imperial units, it is (pounds / inches²) × 703. You do not need to do this math by hand — our BMI calculator does it instantly and also shows the WHO weight category (underweight, normal, overweight, obese) that your result falls into.

Why BMI has limits

BMI does not distinguish between muscle and fat, so very muscular people can show a high BMI while actually being lean. It also does not account for where fat is distributed on the body, which matters for health risk. For a fuller picture, pair BMI with a body fat percentage estimate and a healthy weight range for your height.

What to do with your result

If your BMI falls outside the "normal" range, that is a cue to look closer, not a verdict. Combine it with the ideal weight calculator to see a healthy weight range for your exact height, and the calorie/TDEE calculator if you are planning a weight change — both are free and linked below.