Body composition calculator
BMI calculator
Get your Body Mass Index and weight category from your height and weight. Free, instant, no sign-up.
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NormalWhat is BMI?
Body Mass Index is a simple weight-for-height ratio used as a coarse population screen for under- and overweight. It is quick to compute and universally understood — which is exactly why it is everywhere despite its limits.
How this calculator works
We divide your weight in kilograms by your height in metres squared: BMI = kg / m². Then we map it to the WHO categories — under 18.5 underweight, 18.5–25 normal, 25–30 overweight, 30 and above obese.
The catch
BMI cannot tell muscle from fat. A lean, muscular lifter often reads "overweight" while carrying very little fat. For body composition, pair it with a body-fat estimate or a waist measurement.
FAQ
Is BMI accurate for athletes?
No. BMI does not distinguish muscle from fat, so muscular people are often classified as overweight. Use FFMI or a body-fat estimate instead.
Which BMI categories does this use?
The WHO adult cutoffs: under 18.5 underweight, 18.5 to 24.9 normal, 25 to 29.9 overweight, 30 and above obese.