The Ponderal Index is similar to BMI, but more accurate for those who are very tall or very short.
BMI can overestimate body fat in tall people and underestimate it in short people. The Ponderal Index solves that by cubing your height instead of squaring it.
If you are significantly shorter or taller than average, your Ponderal Index is likely more accurate than your BMI.
What is the Ponderal Index?
The Ponderal Index was developed by a Swiss physician named Fritz Rohrer in 1921, several years before BMI gained widespread use. The only difference is that BMI squares your height, while the Ponderal Index cubes it.
Because the human body is three-dimensional, cubing your height makes more sense when comparing the sizes of different individuals. A healthy Ponderal Index is around 11 and 13.
Ponderal Index Categories
| Category | Ponderal Index | Description |
|---|---|---|
| Underweight | < 11 | Below healthy weight range |
| Ideal | 11-13 | Optimal body proportion |
| Normal | 13-15 | Healthy weight range |
| Overweight | 15-17 | Above healthy weight range |
| Obese | > 17 | Significantly above healthy range |
Ponderal Index vs BMI
In the BMI calculation, height is squared. However, that isn't actually how volume scales. Two people with identical proportions but different heights will get a different BMI result simply because of the height difference. This is of course inaccurate.
The Ponderal Index fixes this by cubing height, which does scale accurately with volume. The result is that the Ponderal Index is more comparable across different heights.
Want to compare? Check your BMI to see if it tells a different story, or try our ideal weight calculator.