BMI, or Body Mass Index, is a rough estimate of the shape of a human body. It only uses two parameters – height (in centimeters) and weight (in kilograms) – and is therefore far from accurate in determining if a person is overweight or underweight. But it does give a fair estimate, so it is still widely used.

The equation for calculating BMI for adults looks like this:




For British and American people that hasn’t adopted the metric system, the equation looks a little different:

BMI for US and UK



With a BMI of over 25, you are considered overweight by the World Health Organization. And with a BMI under 18.5, you are underweight. Remember though that the equation does not take into account if you have a lot of muscles and/or a lot of fat on your body. The result can therefore be misleading for athletic individuals. But for normally built persons, BMI is a pretty good measure for their weight status.

Here’s the complete list of BMI ranges:

Category BMI
Very severly underweight <15
Severly underweight 15 – 16
Underweight 16 – 18.5
Normal 18.5 – 25
Overweight 25 – 30
Moderately obese 30 – 35
Severly obese 35 – 40
Very severly obese >40

You can use this calculator to find out what your BMI is: