BMI Calculator
Body Mass Index in either unit system, plus the weight range considered healthy for your height.
What BMI is — and isn't
BMI is weight divided by height squared (kg/m²), a quick population-level screening number developed in the 1830s. It correlates with body fat across large groups, which is why clinics and insurers use it — but for an individual it knows nothing about muscle, bone density, age, sex or fat distribution. A muscular athlete can read "overweight"; an older adult with low muscle can read "normal" while carrying excess fat.
The standard categories (WHO, adults)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy range |
| 25.0 – 29.9 | Overweight |
| 30.0+ | Obesity |
Some populations use adjusted cutoffs — for example, health agencies recommend a lower overweight threshold (23) for many Asian populations due to different cardiometabolic risk profiles at the same BMI.
Better numbers to pair it with
Waist circumference (risk rises above ~102 cm / 40 in for men, 88 cm / 35 in for women), waist-to-height ratio (keep waist under half your height), blood pressure and bloodwork tell far more than BMI alone. Treat BMI as a rough gauge and trends over time as the signal — and talk to a healthcare professional before acting on any of it.