BMI Calculator
Calculate your Body Mass Index from height and weight and see where it falls on the WHO scale.
Formula
BMI = weight (kg) ÷ height (m)². The result is a single number independent of whether height was measured in centimeters or meters, as long as it is converted to meters first.
Body Mass Index was devised in the 1830s by Belgian statistician Adolphe Quetelet as a population-level measure relating weight to height, not as a diagnostic tool for individuals. It was renamed BMI and popularized in medicine in the 1970s and has since become the default screening number in clinics worldwide.
The World Health Organization divides adult BMI into four bands: below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or above is obese. These thresholds are the same ones used by this calculator.
Common uses
- Understanding the BMI figure printed on an annual physical exam report and knowing which of the four WHO bands it falls into before discussing it with a doctor.
- Setting a realistic weight target for a fitness or diet plan by checking how many kilograms would move your BMI into the next category.
Frequently asked questions
- What BMI is considered normal?
- A BMI from 18.5 to 24.9 is classified as normal weight by the World Health Organization for most adults, regardless of sex.
- Does BMI account for muscle mass?
- No—this is its main limitation. BMI only uses height and weight, so a muscular athlete and a person with excess fat at the same height and weight get an identical score.
- Is BMI accurate for older adults?
- It is less reliable, because older adults naturally lose muscle and can appear "normal" on BMI while carrying more body fat than the number suggests.