BMI calculator
Calculate Body Mass Index.
Questions
What does this tool do?
The BMI calculator works out your Body Mass Index from height and weight in metric (cm and kg) or imperial (feet, inches and pounds) units. The figure updates as you type and lands in one of the four World Health Organization adult bands — underweight, normal, overweight or obese — shown next to the reference ranges. BMI is a quick screening number, not a diagnosis: it does not tell muscle from fat and is not meant for very athletic builds, children or pregnancy.
What is the formula?
BMI is weight in kilograms divided by height in metres squared. The imperial form is 703 × weight in pounds ÷ height in inches squared. Both give the same value.
Which BMI categories are used?
The WHO adult bands: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30 and above obese.
When is BMI not a good measure?
BMI is a population-level screening tool, not a diagnosis. It does not tell muscle from fat and is not meant for very athletic builds, children or pregnancy. Pair it with clinical judgement.