Ponderal Index Body Weight Equation

The Ponderal index is similar to the BMI equation in that it measures the leanness or corpulence of a person based on the person’s height and weight. The main difference between the PI and BMI equation is the cubing rather than squaring of the height in the formula. While BMI can be a useful tool when considering large populations, it is not reliable for determining leanness or corpulence in individuals. Although the PI suffers from similar considerations, the PI is more reliable for use with very tall or short individuals, while BMI tends to record uncharacteristically high or low body fat levels for those on the extreme ends of the height and weight spectrum. Below is the equation for computing the PI of an individual using USC, again using a 5’10”, 160-pound individual as an example:

USC Units: PI =  height (in) ∛mass (lbs)  =  70 ∛160  = 12.89 in ∛lbs SI, Metric Units: PI =  mass (kg) height3 (m)  =  72.57 1.783  = 12.87 kg m3

Ponderal Index Summary

The ponderal index is somewhat comparable to body mass index, but gives a more fair comparison between individuals of different stature. The PI Formula is calculated by taking weight divided by height and raised to the power of 3.