BMI Calculator
Enter your weight and height: your body mass index is calculated instantly, along with the WHO classification and the weight range considered healthy for your height.
Enter your weight and height — the result appears instantly.
The WHO body mass index categories
The World Health Organization groups adult BMI into four main categories: underweight below 18.5, normal weight from 18.5 to 24.9, overweight from 25 to 29.9, and obesity at 30 or above. The formula is your weight in kilograms divided by the square of your height in meters: someone weighing 70 kg (about 154 lb) at 1.75 m (5 ft 9 in) has a BMI of 22.9, comfortably in the normal range. Working in pounds and inches? The same result comes from 703 × weight (lb) ÷ height (in)² — or simply convert: 1 kg ≈ 2.2 lb, 1 inch = 2.54 cm.
What BMI can't tell you
BMI doesn't distinguish muscle from fat: a very muscular athlete can show up as "overweight" while carrying very little body fat. The standard categories also don't apply to children and teenagers or to pregnant women, and should be interpreted with caution after age 65. This tool provides estimates only and is not medical advice — it's no substitute for a doctor or registered dietitian.