Calculate the Conicity Index to describe abdominal adiposity relative to body size. Uses waist circumference, weight, and height as a geometric reference.
The Conicity Index (C-Index) compares a person’s waist circumference with the circumference of a theoretical cylinder that has the same height and weight. Valdez and colleagues proposed it in 1993 as a geometric way to describe central adiposity with an adjustment for body size.
The formula normalizes waist circumference against body size, so two people with the same BMI can still have different values if their fat distribution differs. That makes the index helpful for describing an apple-shaped body pattern versus a more peripheral fat distribution.
Research has associated higher Conicity Index values with cardiovascular and metabolic risk, but the number is best read as a screening reference rather than a diagnosis or treatment rule.
The Conicity Index measures fat distribution rather than total body mass, filling a gap that BMI leaves. Central abdominal fat is metabolically more concerning than peripheral fat, and the C-Index helps describe that pattern. It is especially useful when BMI looks normal but waist size suggests more central adiposity.
Conicity Index = Waist (m) / (0.109 × √(Weight (kg) / Height (m))) The denominator represents the circumference of a cylinder with density 1.05 g/cm³ (close to water) and the same height and mass as the person. The constant 0.109 derives from: 2 × √(π / (1050 × 4)) ≈ 0.109. The index ranges from 1.0 (perfect cylinder) to approximately 1.73 (maximum conicity). Values above 1.25 for men and 1.18 for women are often used as higher-reference bands.
Result: Conicity Index = 1.261
An 85 kg person who is 178 cm tall with a 95 cm waist: C-Index = 0.95 / (0.109 × √(85 / 1.78)) = 0.95 / (0.109 × √47.75) = 0.95 / (0.109 × 6.910) = 0.95 / 0.7532 = 1.261. This is above the common male reference band of 1.25, suggesting greater central adiposity than a lower value would.
The Conicity Index rests on a geometric model. If a person’s weight were distributed uniformly along their height, their body would resemble a cylinder, and their waist circumference would match the calculated cylinder circumference. As fat accumulates centrally, the body shape deviates from this cylinder toward a more cone-like form, and the ratio of actual waist circumference to the cylinder’s circumference increases.
Large cohort studies have shown the Conicity Index to be associated with cardiometabolic risk. Some analyses have found it performs comparably to waist-to-hip ratio and can add information beyond BMI because it specifically captures central fat patterning.
BMI measures total body mass relative to height and cannot distinguish between peripheral and central fat deposition. Two individuals with the same BMI — one apple-shaped and one pear-shaped — can have different metabolic risk profiles. The Conicity Index is one way to describe that difference.
Optimal C-Index cut-offs vary by ethnicity. South Asian and East Asian populations may have elevated risk at lower values due to differences in body fat distribution. Athletes with well-developed core musculature may have higher waist measurements that inflate the C-Index without necessarily reflecting excessive fat. As with all anthropometric tools, clinical context is essential.
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This page calculates the geometric conicity index from waist circumference, height, and weight, then places the result next to the usual sex-specific reference bands. The output is intended as a body-shape reference, not as a diagnosis. Thresholds and risk context should be interpreted alongside BMI, waist circumference, and the rest of the clinical picture.
The Conicity Index (C-Index) is an anthropometric measure that describes how much a person’s body shape deviates from a perfect cylinder. A cylindrical body has a C-Index near 1.0, while a more cone-shaped body has higher values. It was proposed by Valdez et al. as a way to describe abdominal adiposity.
Commonly cited reference bands are below 1.25 for men and below 1.18 for women. These are broad context bands rather than universal diagnostic cut-offs, and optimal thresholds can vary by ethnicity and study population.
Waist-to-hip ratio compares waist and hip circumferences but ignores height and weight. The Conicity Index normalizes waist circumference against a theoretical cylinder derived from height and weight, so it can be compared across different body sizes.
Theoretically no. The maximum value is √3 ≈ 1.732, which would correspond to an extreme double-cone shape. In practice, observed values are much lower.
Higher conicity values have been associated with cardiovascular and metabolic risk in cohort studies. It is best treated as one screening reference alongside BMI, waist circumference, and clinical context.
Yes. The C-Index can help describe central adiposity in people whose BMI looks normal but whose waist suggests more abdominal fat. It is a descriptive reference, not a diagnosis.
Valdez, Seidell, Ahn, and Weiss introduced the Conicity Index in a 1993 paper in the International Journal of Obesity.
Reducing waist circumference is the most direct approach. Regular aerobic exercise and dietary changes that reduce abdominal fat will usually lower the index over time.