BMI Calculator — Check Your Body Mass Index
Calculate your Body Mass Index (BMI) from height and weight, in metric or imperial units.
About the BMI Calculator
Body Mass Index (BMI) is a screening measurement calculated from height and weight. It's used by doctors and health organizations as a quick, low-cost way to categorize a person's weight as underweight, normal weight, overweight, or obese, using the formula BMI = weight (kg) ÷ height (m)².
This calculator accepts both metric (kilograms and centimeters) and imperial (pounds, feet and inches) units, so you don't need to convert anything yourself. Enter your height and weight and it instantly returns your BMI value along with the standard World Health Organization weight category it falls into.
Worked example
Example: a person who is 1.75 m tall and weighs 70 kg has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls in the 'normal weight' range of 18.5–24.9.
Frequently asked questions
- What is a healthy BMI range?
- For most adults, the World Health Organization defines 18.5–24.9 as the 'normal weight' range, below 18.5 as underweight, 25–29.9 as overweight, and 30+ as obese.
- Is BMI accurate for everyone?
- BMI is a useful population-level screening tool, but it doesn't distinguish between muscle and fat mass. It can misclassify very muscular people as overweight and may be less accurate for older adults, children, or pregnant women. It should be one data point, not a standalone diagnosis.
- Does BMI differ for men and women?
- The standard BMI formula and category ranges are the same for adult men and women, though body composition naturally differs between sexes, which is part of why BMI is only a screening estimate.
- How often should I check my BMI?
- There's no strict rule — many people check every few months or after a significant weight change. BMI is meant to track general trends over time rather than day-to-day fluctuations.