BMI Calculator
Calculate your Body Mass Index in metric or imperial units, see your BMI category and the healthy weight range for your height.
About the BMI Calculator
Body Mass Index is a quick screening measure that compares weight to height. Enter yours in kilograms and centimetres or pounds and feet to see your BMI, the category it falls in and the weight range considered healthy for your height.
How to use it
- Choose metric or imperial units.
- Enter your height and weight.
- Read your BMI, category and healthy weight range.
The BMI formula
BMI is weight in kilograms divided by height in metres squared. Someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which is in the healthy range. For that height, a BMI of 18.5 to 24.9 corresponds to a weight of about 56.7 to 76.3 kg. Imperial measurements are converted to metric first.
What the categories mean
The World Health Organization uses under 18.5 for underweight, 18.5–24.9 for a healthy weight, 25–29.9 for overweight and 30 or more for obesity. WHO guidance for Asian populations suggests lower action points, with risk rising from a BMI of about 23, and many South Asian health services use those lower cut-offs.
Limits of BMI
BMI doesn't measure body fat directly, so muscular people can score as overweight and older adults with low muscle mass can score as healthy while carrying excess fat. Waist measurement is a useful second check. BMI is not suitable for children, teenagers or during pregnancy; speak to a doctor for personal advice.
Frequently asked questions
What is a healthy BMI?
For most adults the World Health Organization defines 18.5 to 24.9 as a healthy range, 25 to 29.9 as overweight and 30 or more as obese. Some health bodies use lower cut-offs for people of Asian descent.
Is BMI accurate?
It is a population-level screening tool. It does not distinguish muscle from fat, so athletes may score high. Talk to a doctor for a personal assessment.
Can children use this calculator?
No. Children and teenagers need age- and sex-specific BMI percentiles.