How to calculate your BMI
- Choose metric (cm and kg) or imperial (feet/inches and pounds).
- Enter your height and weight.
- Read your BMI and the category it falls into on the gauge.
- See the healthy weight range for your height.
The BMI formula
Body Mass Index is your weight in kilograms divided by the square of your height in metres: BMI = kg ÷ m². In imperial units it is 703 × pounds ÷ inches². For example, someone 1.75 m tall weighing 70 kg has a BMI of 70 ÷ (1.75 × 1.75) ≈ 22.9.
BMI categories for adults
Under 18.5 is classed as underweight, 18.5 to 24.9 as a healthy weight, 25 to 29.9 as overweight, and 30 or above as obese. These are the World Health Organization’s ranges for adults aged 20 and over. Some health bodies use lower cut-offs for people of South Asian, Chinese and other Asian backgrounds.
Limitations of BMI
BMI is a quick screening number, not a diagnosis. It doesn’t distinguish muscle from fat, so athletes can score as “overweight”, and it says nothing about where fat is carried. It is not designed for children, teenagers or pregnant women. Talk to a doctor if you are concerned about your weight.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight.
Is BMI accurate for athletes?
Not always. Muscle is denser than fat, so muscular people can have a high BMI while having low body fat.
Is my data stored?
No. The calculation runs in your browser and nothing you enter is sent anywhere.
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