How to use the bMI calculator
Choose metric or imperial, then enter your weight and height. BMI is a quick screening number that compares weight with height. For adults, the World Health Organization groups it as underweight (below 18.5), healthy weight (18.5 to 24.9), overweight (25 to 29.9) and obesity (30 and above).
BMI does not measure body fat directly. It can overstate fat in muscular people and understate it in older adults, and the ranges are different for children and teenagers. Treat it as a starting point for a conversation with a health professional.
The formula
BMI = weight in kg ÷ (height in m)²
In imperial units: BMI = 703 × weight in lb ÷ (height in inches)².
Worked example
Someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9, which is in the healthy weight range.
This calculator gives a general estimate for adults. It is not medical advice. Talk to a doctor or other qualified health professional about your own situation.
Common questions
Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so a muscular person can have a high BMI with little body fat. A body fat estimate is a useful second check.
Does BMI apply to children?
Children and teenagers are assessed with age and sex specific growth charts, not the adult ranges shown here.
Are the ranges the same for everyone?
Some health bodies use lower thresholds for people of Asian descent, because health risks can rise at a lower BMI.