What makes a BMI calculator "adult"?
For adults, BMI uses a single set of numeric cut-offs regardless of age or sex: under 18.5 is underweight, 18.5–24.9 is the WHO healthy band, 25–29.9 is overweight, and 30 and over is obesity (with sub-classes I, II, and III at 35 and 40). Children and teens are different — see the child BMI calculator. The adult cut-offs were chosen in 1995 by the World Health Organization and have been the international standard ever since.
Asian adult BMI cut-offs
A 2004 WHO Expert Consultation (published in The Lancet) reviewed evidence that, for many Asian populations, the risk of type 2 diabetes and cardiovascular disease starts climbing at lower BMIs than for European-descended cohorts. Several Asian countries now use lower thresholds: overweight ≥ 23 and obese ≥ 27.5. Switch on Asian BMI in the calculator to use these cut-offs.
How to read the result
The big number is your BMI to one decimal place. The gauge sweeps the four WHO bands in colour. Underneath, we show BMI Prime (your BMI divided by 25), Ponderal Index (kg/m³), body-fat percentage, healthy weight range, ideal weight (Devine), lean body mass (Boer), BMR (Mifflin–St Jeor) and TDEE at five activity levels, plus the waist-to-height ratio if you provide waist.
When adult BMI is not enough
BMI uses only height and weight, so it cannot tell muscle from fat, bone from water, or where on the body weight is carried. For cardiometabolic risk, pair it with waist circumference (or our waist-to-height calculation), fasting glucose, lipids and blood pressure — and review with a clinician.
Next steps
- Male BMI calculator / Female BMI calculator
- Asian BMI calculator
- CDC BMI calculator for child/teen percentiles
- BMI charts and tables