BMI Calculator
Enter your weight and height to get your Body Mass Index and see where it sits in the WHO adult categories.
What is BMI?
Body Mass Index (BMI) is a simple screening number that relates your weight to your height. Doctors and health organisations use it as a first-pass indicator of whether an adult's weight may be putting their health at risk. It is not a diagnosis — it does not measure body fat directly — but it correlates well enough with risk at population level that it has remained the standard first check for decades.
Worked example: a person who weighs 70 kg and is 1.75 m tall: 1.75² = 3.0625, and 70 ÷ 3.0625 = 22.9 — comfortably inside the healthy 18.5–24.9 band. The same person at 90 kg would have a BMI of 29.4, at the top of the overweight band.
If your result surprises you, remember the limitations: BMI does not account for muscle mass, bone density, age, sex or where fat is carried. Treat it as a starting point for a conversation about health — ideally paired with waist measurement and professional advice — never as a final verdict.
Frequently asked questions
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is classified as a healthy weight by the World Health Organization. Below 18.5 is underweight, 25.0–29.9 is overweight, and 30 or above is obese. These are screening ranges, not diagnoses.
What is the BMI formula?
BMI = weight in kilograms divided by height in metres squared. In imperial units, BMI = 703 × weight in pounds divided by height in inches squared. Both give the same result.
Is BMI accurate for athletes?
BMI can misclassify muscular people, because it cannot distinguish muscle from fat — a bodybuilder may score 'overweight' with low body fat. It is a quick population screening tool, not a complete measure of health.
Does BMI apply to children?
Not directly. For children and teenagers, BMI is compared against growth-chart percentiles for their age and sex. The adult categories on this page apply to people aged 20 and over.