What Is a BMI Calculator?
A Body Mass Index (BMI) calculator is a biological screening tool designed to estimate general body fatness based on an adult's height and weight. By dividing body weight by height squared, the calculator slots individuals into standardized categories: Underweight, Normal Weight, Overweight, or Obese.
While BMI does not measure body composition directly, it is highly useful for large-scale epidemiological monitoring and provides a quick health indicator. However, because it relies purely on weight, it does not distinguish between muscle tissue and fat mass. Thus, it can misclassify muscular athletes or bodybuilders as overweight.
Formula
The Body Mass Index is calculated using two primary mathematical variants depending on the system of measurement:
How to Use This Calculator
- Select Units: Choose between "Metric (kg/cm)" and "Imperial (lbs/ft)" using the toggle button at the top of the interface.
- Input Weight: Type your current weight in kilograms or pounds.
- Input Height: Type your height in centimeters or feet and inches.
- Analyze Output: The widget calculates your BMI in real time, displays your category (WHO classification), and flags your placement on a color-coded gauge.
Worked Example
Let's calculate the BMI of an individual who weighs 75 kilograms and stands 180 centimeters (1.8 meters) tall.
1. Convert height to meters: 180 cm = 1.8 meters.
2. Square the height: 1.8 × 1.8 = 3.24 m².
3. Divide weight by squared height: 75 ÷ 3.24 = 23.15.
4. The calculated Body Mass Index is 23.2.
5. Since 23.2 is between 18.5 and 24.9, the classification is Normal Weight.