Body composition

Calculate BMI

The body mass index relates weight to height. Quick to calculate, but only of limited value for strength athletes.

For adults. Different limits apply to children and teenagers.

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How it works

BMI is body weight in kilograms divided by height in meters squared. The World Health Organization (WHO) uses it to sort adults into weight classes.

In addition, the calculator shows which weight corresponds to a BMI of 18.5 to 24.9 at your height.

How to use your result

BMI does not distinguish between muscle and fat. With a lot of muscle mass you quickly land in the overweight range even though your body fat percentage is low. For strength athletes, body fat percentage and FFMI therefore say more.

For tracking a Lean Bulk or Cut, BMI hardly helps: it moves exactly like your weight. Better to watch trend weight and waist circumference.

Categories by WHO

BMICategory
< 18.5Underweight
18.5 - 24.9Normal weight
25.0 - 29.9Overweight (pre-obesity)
30.0 - 34.9Obesity class I
35.0 - 39.9Obesity class II
≥ 40.0Obesity class III

Formula and source

BMI = weight (kg) ÷ height (m)²

Categories after World Health Organization (2000): Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894.

Frequently asked questions

Only to a very limited degree. BMI only knows weight and height. With a lot of muscle mass it quickly shows overweight even though body fat percentage is low. Body fat percentage, FFMI and waist circumference say more.

According to the WHO, for adults a BMI of 18.5 to 24.9 counts as normal weight, 25 to 29.9 as overweight and 30 and above as obesity. This classification does not take age, sex or build into account.

For strength athletes, a combination of body fat percentage, FFMI and waist circumference. Together they show whether your weight comes more from muscle or from fat.

No. For children and teenagers, age- and sex-specific percentiles are used. This calculator is meant for adults.

All results are estimates and do not replace advice from a doctor or dietitian.

Related calculators

Body fat calculator Estimate with the US Navy tape measure method. FFMI calculator Fat-free mass relative to height, after Kouri 1995. Ideal weight calculator An estimated range from common formulas, clearly labelled as an estimate.