FITsociety IO
Try for free

BMI explained

BMI calculator

Calculate your Body Mass Index from your weight and height, and read how to interpret the result in context.

Calculate your BMI

Enter height in centimeters and weight in kilograms.

What is BMI?

BMI stands for Body Mass Index. It is a simple screening value that compares body weight with height. For adults, it is often used as a first indication of whether weight is low, in a healthy range, high, or in the obesity range.

How BMI is calculated

The metric BMI formula divides weight in kilograms by height in meters squared.

BMI = weight (kg) / height (m)2

How to read the result

For adults, a BMI below 18.5 is usually classed as underweight. A BMI from 18.5 to below 25 is in the healthy range, 25 to below 30 is overweight, 30 to below 40 is obesity, and 40 or higher is severe obesity.

BMI is not the whole picture

BMI can be useful as a starting point, but it does not decide your health on its own.

  • BMI does not measure muscle mass, bone density, body fat percentage, or fat distribution.
  • Age, sex, training level, pregnancy, medical history, and personal context can change how a result should be interpreted.
  • For children and teenagers, BMI is interpreted differently and should use age- and sex-specific growth references.
  • Ask a qualified health professional if you need personal advice about your weight, health, or training goals.