The Body Mass Index (BMI) formula was developed by Belgium statistician Adolphe Quelet(1796-1874), and was known as the Quetelet Index. BMI is also referred to as 'body mass indicator'. BMI is an internationally used measure of obesity.

Body mass index calculation is very straightforward. Calculating body mass index requires only two measurements, height & weight.

Many people use body mass index (BMI) to determine whether or not they fall within a healthy weight range. However, the accuracy of BMI in relation to actual levels of body fat is easily distorted by such factors such as muscle mass, bone structure, fitness level, gender and ethnicity, which BMI does not take into account.

Mesomorphs have a greater amount of bone and muscle mass compared to endomorphs and therefore tend to have a higher BMI. Thus, although they have a higher BMI, it may be the case that the mesomorph actually has a lower body fat percentage than the endomorph, since muscle and bone mass weighs more than fat tissue. Similarly, an ectomorphic individual could conceivably receive an unhealthily low reading, when in fact their body type makes them naturally thin no matter what they eat. Thus, ectomorphs may be able to obtain healthy readings even when their body fat percentage is higher than recommended, as their low lean mass will lower the BMI.