Calculate the Corpulence Index (CI) — the reciprocal of the Ponderal Index. Compare CI with BMI for a height-independent body mass assessment.
The Corpulence Index (CI) is a body proportionality metric closely related to the Ponderal Index. While the Ponderal Index is defined as mass / height³, some references define the Corpulence Index as height³ / mass (the reciprocal), and others treat it as an identical measure under an alternative name. This calculator computes both interpretations so you can use whichever convention your reference material follows.
Like the Ponderal Index, the Corpulence Index uses the cube of height rather than the square, providing a more height-independent assessment of body build than BMI. This is especially useful when comparing individuals of vastly different statures, from children to very tall adults, and across populations with different average heights.
The term "corpulence" itself dates to Adolphe Quetelet's 19th-century anthropometric work, where he used it to describe body build relative to stature. Today the Corpulence Index appears most frequently in European epidemiological literature and in studies comparing multiple body-mass indices for predictive accuracy in cardiovascular and metabolic disease.
The Corpulence Index offers an alternative perspective on the same data that BMI uses, with the advantage of a height-cubed denominator. This makes it useful for identifying height-related biases in BMI assessments. By computing CI alongside BMI and the Ponderal Index, you can see how different mathematical treatments of the same height and weight data yield different conclusions — particularly at the extremes of the height distribution.
Corpulence Index (as mass/height³): CI = Mass (kg) / Height (m)³ This is identical to the Ponderal Index in kg/m³. Reciprocal form: CI′ = Height (m)³ / Mass (kg) BMI for comparison: BMI = Mass (kg) / Height (m)² Normal adult CI (mass/height³): approximately 11–15 kg/m³ Normal adult CI′ (height³/mass): approximately 0.067–0.091 m³/kg
Result: CI = 14.2 kg/m³ (Normal)
A person 170 cm (1.70 m) tall weighing 70 kg has CI = 70 / 1.70³ = 70 / 4.913 = 14.2 kg/m³. The reciprocal form is 4.913 / 70 = 0.0702 m³/kg. Their BMI is 70 / 1.70² = 24.2. All three metrics classify this person as normal weight, though the CI value is less familiar to most people than BMI.
The word "corpulence" — from the Latin corpulentia, meaning fatness — entered anthropometric vocabulary through Adolphe Quetelet's 19th-century work on human body measurements. Quetelet himself developed what we now call BMI, and various researchers later proposed height-cubed alternatives under names including the Corpulence Index, Ponderal Index, and Rohrer Index. The proliferation of names for essentially the same mathematical concept has caused confusion in the literature.
The relationship between CI and BMI is straightforward: CI = BMI / height. This means that for a given BMI, taller people will have lower CI values and shorter people will have higher CI values. At a height of exactly 1 meter (hypothetical), CI and BMI would be identical. As height increases, CI decreases relative to BMI, which is why CI classifies tall people as leaner than BMI does — a correction many anthropometrists consider more accurate.
Comparative studies have tested CI (along with PI, BMI, and waist circumference) as predictors of metabolic syndrome, type 2 diabetes, and cardiovascular events. Results are mixed: in most general-population studies, CI and BMI perform similarly, but in height-diverse cohorts (e.g., multi-ethnic studies), height-cubed indices sometimes outperform BMI. No consensus has emerged to replace BMI, but CI contributes to the broader conversation about optimal body-mass metrics.
For everyday health monitoring, BMI remains the most practical choice because of its widespread familiarity, established clinical thresholds, and vast supporting literature. CI is best thought of as a complementary metric — useful for research, for populations where height bias matters, and for individuals at the extremes of the height spectrum who suspect BMI may be misclassifying them.
The Corpulence Index is a body-mass metric that uses height cubed in its calculation. Depending on the source, it may be defined as mass/height³ (identical to the Ponderal Index) or as height³/mass (the reciprocal). Both forms aim to provide a more height-independent measure of body build than BMI.
When defined as mass/height³, yes — it is numerically identical. Some authors use "Corpulence Index" and "Ponderal Index" interchangeably, while others define the Corpulence Index as the reciprocal (height³/mass). This calculator shows both forms to eliminate ambiguity.
For adults, the normal range in the mass/height³ form is approximately 11–15 kg/m³. In the reciprocal form (height³/mass), normal is approximately 0.067–0.091 m³/kg. These ranges correspond roughly to a BMI of 18.5–24.9.
CI uses height cubed, which better reflects how body volume scales with height. BMI's height-squared denominator causes it to overestimate adiposity in tall individuals and underestimate it in short individuals. CI avoids this systematic height bias, making it more equitable for height-diverse populations.
The Corpulence Index appears primarily in European epidemiological research and comparative anthropometric studies. It is less commonly used in routine clinical practice than BMI, but it shows up in academic papers evaluating which body-mass metric best predicts cardiovascular or metabolic outcomes.
Some studies have found that height-cubed indices correlate similarly to BMI with cardiovascular risk factors, and may be slightly better predictors in height-diverse populations. However, BMI has far more outcome data supporting its clinical thresholds, which is why it remains the default screening tool in most guidelines.
Yes — in fact, height-cubed indices are considered theoretically more appropriate for children, whose body proportions change rapidly during growth. The Rohrer Index (a scaled version of CI) has been used in Japanese and European pediatric screening programs. Age- and sex-specific reference values should be used for children.
CI (kg/m³) = BMI / Height(m). So for a person 1.75 m tall with a BMI of 24, CI = 24 / 1.75 = 13.7 kg/m³. Conversely, BMI = CI × Height(m). This simple relationship shows that BMI and CI differ only by a factor of height.