Ponderal Index Calculator
Calculate your Ponderal Index (PI), an alternative to BMI that uses height cubed instead of height squared. PI may be more appropriate for very tall or short individuals.
Understanding Ponderal Index
The Ponderal Index (PI), also known as the Corpulence Index or Rohrer Index, relates body mass to height using the cube of height rather than the square. It's particularly used in neonatal assessment and may provide a more accurate measure for individuals at height extremes.
PI = 75 ÷ (1.80)³ = 75 ÷ 5.832 = 12.86 kg/m³
For comparison, BMI = 75 ÷ (1.80)² = 23.1 kg/m²
PI vs BMI: Key Differences
When to Consider PI Over BMI
BMI was designed for population studies and assumes a standard height range. Very tall people tend to have artificially high BMIs, while very short people have artificially low BMIs. The Ponderal Index adjusts for this by using height³, making it potentially more accurate at height extremes.
Interpretation
A normal Ponderal Index for adults is approximately 11–15 kg/m³. Values below 11 suggest underweight, while values above 15 may indicate overweight. However, interpretation should consider individual factors.
Frequently Asked Questions
The Ponderal Index is a measure of body mass relative to height cubed. It's an alternative to BMI that may be more accurate for very tall or short people.
Body volume scales approximately with height cubed, not squared. Using height³ better accounts for how body mass should relate to a three-dimensional body.
PI is widely used in neonatal medicine to assess newborn nutritional status and identify growth restriction. It's also used in anthropometric research.
For adults, normal PI is roughly 11-15 kg/m³. For newborns, normal is approximately 24-28 kg/m³.