BMI calculator
Find your body mass index and where it sits on the healthy range.
Your BMI
BMI is a quick screen, not a diagnosis — it doesn't account for muscle, frame, or body composition.
What BMI is and how it is calculated
Body Mass Index (BMI) is a quick screening number that compares your weight to your height. It does not measure body fat directly, but for most adults it gives a useful, fast estimate of whether your weight sits in a healthy range.
The formula
imperial: BMI = 703 × weight(lb) ÷ height(in)²
BMI categories
- Under 18.5 — underweight
- 18.5 to 24.9 — healthy weight
- 25 to 29.9 — overweight
- 30 and above — obese
Example: someone 1.75 m tall weighing 70 kg has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which is in the healthy range. BMI is a general screen, not a diagnosis, and is best discussed with a doctor.
Frequently asked questions
How is BMI calculated?
Divide your weight in kilograms by your height in metres squared. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared.
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is in the obese range.
Is BMI accurate?
BMI is a helpful screen but not perfect. It does not distinguish muscle from fat, so very muscular people can read high, and it does not account for age, sex, or where fat is stored. Treat it as one signal among several.
Is BMI different for men and women?
The formula and adult categories are the same for men and women. Body composition differs between sexes, which is one reason BMI is only a general guide.
How can I move into a healthy BMI range?
Gradual changes to diet and activity that create a modest calorie deficit are the safest path. A doctor or registered dietitian can help you set a realistic target.