How BMI is calculated
BMI = weight in kilograms divided by height in metres squared. For adults the WHO uses these ranges: below 18.5, 18.5–24.9, 25–29.9 and 30 or more.
What BMI does not show
- Muscle: strong, muscular people often have a BMI above 25 without extra fat.
- Where fat is stored: waist size says more about health risk.
- Age, sex and ethnicity: the same BMI can mean different things for different people.
For a better picture, use BMI together with waist size or the body fat calculator.
Questions and answers
Is BMI accurate for athletes?
Not very. Muscle is heavy, so athletes often have a high BMI. Body fat percentage describes them better.
Can children use this calculator?
No. For children and teenagers BMI is judged with age and sex percentiles, which a doctor or school nurse can check.
How it is calculated: sources
- World Health Organization. Body mass index (BMI) classification for adults.
- Nuttall FQ. Body mass index: obesity, BMI, and health — a critical review. Nutr Today. 2015;50(3):117–128.
Gymvert gives general information for healthy adults. It is not medical advice. If you have a health condition, are pregnant, or are unsure, talk to a doctor before changing your training or diet.