Conicity Index Calculator
Calculate the Conicity Index (C-Index) from waist, weight and height to gauge central fat distribution.
How to use this tool
- Measure your waist at the navel in centimetres.
- Enter your weight in kilograms.
- Enter your height in centimetres.
- Read your Conicity Index and screening interpretation.
The Conicity Index calculator estimates how much your body tapers toward an abdominal (apple) shape using waist, weight and height — a marker of central fat that needs no hip measurement.
Formula
C-Index = waist (m) ÷ (0.109 × √(weight (kg) ÷ height (m)))
The constant 0.109 converts the volume of a reference cylinder so the index is dimensionless. Waist and height are in metres and weight in kilograms.
How it works
The Conicity Index was proposed by Valdez in the Journal of Clinical Epidemiology (1991). It compares a person's waist to the waist of a hypothetical cylinder of the same height and weight; the more the body tapers toward a double-cone (apple) shape, the higher the index. Because it builds in weight and height, it does not require a separate hip measurement like the waist-to-hip ratio.
Typical values fall roughly between 1.0 and 1.5. There is no universal clinical cut-off — reported thresholds vary by population and study — so the labels here are a simple screening signal, not a diagnosis.
This calculator is provided for general information and education only and is not medical advice. Body-shape indices are screening estimates, not diagnoses. Always consult a qualified healthcare professional before making decisions about your health.
Worked example
Waist 90 cm, weight 80 kg, height 175 cm
- Convert to metres: waist = 0.90 m, height = 1.75 m
- weight ÷ height = 80 ÷ 1.75 = 45.7143
- √45.7143 = 6.76123
- 0.109 × 6.76123 = 0.736974
- waist ÷ that = 0.90 ÷ 0.736974 = 1.22128
- Round to two decimals = 1.22
Conicity Index = 1.22 (Lower central-fat signal)
Conicity Index — typical interpretation
| C-Index range | General interpretation |
|---|---|
| < 1.15 | Low central-fat signal |
| 1.15 – 1.24 | Moderate / lower central-fat signal |
| 1.25 – 1.34 | Elevated central-fat signal |
| ≥ 1.35 | High central-fat signal |
Key terms
- Conicity Index (C-Index)
- A dimensionless measure of central fat distribution comparing the waist to a reference cylinder of equal height and weight.
- Central obesity
- Excess fat concentrated around the abdomen, associated with greater metabolic and cardiovascular risk than peripheral fat.
- Reference cylinder
- The hypothetical cylinder of the same height and weight against which the actual waist is compared in the conicity formula.
Frequently asked questions
- What is a normal Conicity Index?
- Most adults fall between about 1.0 and 1.5. Thresholds differ between studies and populations, so the index is best used to track change over time rather than as a hard cut-off.
- How is the Conicity Index different from waist-to-hip ratio?
- The C-Index uses weight and height instead of a hip measurement, so it describes abdominal shape relative to overall body size without needing a second circumference.
- Why is there a 0.109 constant?
- 0.109 comes from the geometry of the reference cylinder and makes the index unitless so values are comparable across people.