BMI Calculator
Calculate your Body Mass Index from height and weight, in metric or imperial units. See your BMI value and which category it falls into.
How to use
How BMI is calculated
BMI = weight (kg) ÷ height (m)². For imperial, BMI = 703 × weight (lb) ÷ height (in)². The same formula is used worldwide for adults aged 20 and over.
The standard categories
Under 18.5 is underweight, 18.5–24.9 is healthy, 25–29.9 is overweight, and 30 or above is obese — ranges set by the World Health Organization.
What BMI does not tell you
BMI is a rough screening tool. It cannot tell muscle from fat, so very muscular people can read as overweight. It is also less reliable for children, older adults and pregnant women.
BMI was devised in the 1830s by Belgian mathematician Adolphe Quetelet — it was originally called the Quetelet Index and was never intended to measure individual health, only to describe populations.
Frequently asked questions
Is BMI accurate?
BMI is a useful population-level screening tool but a blunt instrument for individuals. It cannot tell muscle from fat, so athletes may register as overweight while someone with low muscle mass may register as healthy despite high body fat. Use it alongside other measures like waist circumference.
What is a healthy BMI range?
For most adults a BMI between 18.5 and 24.9 is considered healthy by the World Health Organization. Below 18.5 is underweight and 25 or above is overweight. These thresholds are the same for men and women but do not apply to children.
Does BMI differ for men and women?
The BMI formula and adult categories are identical for men and women. However, women naturally carry more body fat than men at the same BMI, so the number alone does not reflect body-composition differences between the sexes.