BMI Calculator
Your Body Mass Index: instantly, as you type.
A healthy weight for your height: 56.7–76.3 kg
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What is BMI?
Body Mass Index (BMI) is a simple measure that relates your weight to your height. It is calculated as weight in kilograms divided by height in metres squared (kg/m²), and it is the most widely used quick check of whether a person's weight is in a healthy range.
BMI by country
The same BMI does not mean the same health risk everywhere. At an identical BMI, people of Asian descent carry on average 3–5 percentage points more body fat, and more of it as visceral fat around the organs, than white European populations, so diabetes and cardiovascular risk appear at lower BMI values. For this reason a 2004 WHO expert consultation proposed lower action points for Asian populations.
| Interpretation | Overweight | Obese | Commonly used in |
|---|---|---|---|
| WHO (international) | ≥ 25 | ≥ 30 | USA, Europe and most of the world |
| Asia-Pacific | ≥ 23 | ≥ 25 | South Korea, Japan, India, Singapore and other Asian countries |
| China | ≥ 24 | ≥ 28 | Mainland China |
Limitations
BMI does not measure body fat directly and cannot tell muscle from fat. A muscular athlete can have an 'overweight' BMI while being perfectly healthy, and a normal BMI can hide low muscle mass or excess abdominal fat.
Categories
The World Health Organization defines these ranges for adults aged 20 and over:
| Category | BMI |
|---|---|
| Underweight | < 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25 – 29.9 |
| Obese | ≥ 30 |
History
The formula was devised in the 1830s by Adolphe Quetelet, a Belgian astronomer and statistician, and was long known as the Quetelet Index. The name 'body mass index' was coined in 1972 by the American physiologist Ancel Keys.
Formula
BMI is weight in kilograms divided by the square of height in metres: BMI = kg/m². For example, 70 kg at 1.75 m gives 70 / (1.75 × 1.75) = 22.9.
Frequently asked questions
What is a normal BMI?+
For adults, a BMI between 18.5 and 24.9 is considered normal weight according to the World Health Organization.
How is BMI calculated?+
BMI equals your weight in kilograms divided by the square of your height in metres: BMI = kg/m². For example, 70 kg at 1.75 m gives 70 / (1.75 × 1.75) = 22.9.
Is BMI accurate for everyone?+
No. BMI does not distinguish muscle from fat, so very muscular people may be classified as overweight while being healthy. It is also not suitable for children, pregnant women, or the very elderly without adjusted charts.