How is BMI calculated?

Weight in kilograms divided by height in metres squared. In imperial units: 703 × weight in pounds ÷ height in inches squared.

Is BMI accurate for everyone?

No. It can overestimate for muscular people and underestimate for people with low muscle mass. It is a starting point for a conversation.

What BMI ranges does the WHO use?

Under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and over obese.

All tools

BMI Calculator

Enter your weight and height to get your body mass index. BMI is a quick screening measure, not a diagnosis.

Your Measurements

Weight (kg)

Height (cm)

Calculate Body Mass Index from height and weight — used by health professionals and individuals to screen weight categories.

Formula

Metric: BMI = weight(kg) ÷ height(m)². Imperial: BMI = 703 × weight(lbs) ÷ height(in)².

Reference Values

•BMI 18.5–24.9 = Normal weight
•BMI 25–29.9 = Overweight
•BMI ≥ 30 = Obese

FAQ

Common questions about BMI Calculator

How we calculate this

We use the standard published formula for this calculation, and we show the working so you can check it.

Spotted a mistake? Tell us and we'll check it within a few days. See how we check our calculators.

Medical disclaimer

This tool gives a general estimate for information only. It is not medical advice and cannot diagnose a condition. Talk to a doctor, midwife or other qualified professional about your own situation.