Conicity Index
The conicity index compares your waist measurement with the waist a cylinder of your own height and weight would have, so a higher number means fat is concentrated at the middle.
Plain English
Patient-Friendly Explanation
Waist circumference on its own has a practical problem. A tall, heavy person and a short, light person can share the same waist measurement, yet the fat is distributed differently relative to the size of the body carrying it. The conicity index was designed to correct for that. It compares your actual waist with the waist that a cylinder of your height and weight would have. If your body were perfectly cylindrical, with fat spread evenly, the index would sit near 1.1. As fat gathers at the middle, the shape changes from a cylinder towards a double cone, which is where the name comes from, and the number rises. The arithmetic is simple: your waist in metres, divided by 0.109, divided by the square root of your weight in kilograms divided by your height in metres. It uses three measurements you already know, needs no blood test, and takes a minute with a calculator. Higher values are consistently found in people with metabolic syndrome, high blood pressure and type 2 diabetes. The catch is that, unlike BMI or the waist-to-height ratio, there is no single agreed cut-off. Research groups have proposed values mostly between about 1.18 and 1.27, depending on sex, population and what is being predicted, and in at least one large Asian study the index performed less well than the simpler waist-to-height ratio. So the conicity index is not a number to memorise. It is a number to follow: if it falls as your waist falls, the fat that matters is coming off.
Medical
Clinical Definition
The conicity index (C index) was proposed by Valdez in 1991 as a model-based index of abdominal adiposity, calculated as waist circumference in metres divided by 0.109 multiplied by the square root of body weight in kilograms divided by height in metres, giving units of m3/2 per kg1/2. The constant 0.109 is derived from an assumed average human body density of 1,050 kg per cubic metre and represents the external circumference a cylinder of the same height and weight would have. The index formalises the observation that central fat accumulation changes body shape from a cylinder towards a double cone, and its theoretical advantage over raw waist circumference and over fixed waist ratios is that the denominator is scaled to the individual height and weight, permitting comparison across very different body sizes. Higher values are associated with central adiposity, insulin resistance, dyslipidaemia, hypertension, metabolic syndrome type 2 diabetes and cardiovascular risk scores across populations, and the index has been linked in cross-sectional NHANES analyses to non-metabolic outcomes such as hearing impairment. Its principal limitation is the absence of universally agreed cut-off points: reported thresholds range from about 1.18 to 1.27 according to sex, ethnicity and the criterion used, with population means typically between 1.15 and 1.25. In a Korean study of 110,253 Health Examinees the optimal cut-off was 1.20 in men and 1.18 in women, but discriminative performance for metabolic abnormalities was the lowest of the anthropometric indices tested, with an area under the receiver-operating characteristic curve of 0.616 in men and 0.645 in women against 0.677 and 0.691 for the waist-to-height ratio; studies that derive cut-offs against metabolic syndrome in other populations report higher values of roughly 1.25 to 1.27. The index is unaffected by height in the way BMI is, is reproducible from three routine measurements, and requires no laboratory test, but because it is a ratio it can give counterintuitive readings in very muscular or very wasted individuals. It therefore contributes most as a serial within-person measure and as a screening or research adjunct alongside waist circumference, waist-to-height ratio and formal body composition assessment, and it does not replace them.
Key Insight
Why It Matters
The conicity index earns its place by scaling the waist to your own height and weight, so it tracks the shape change that matters as the tape falls, but with no single agreed cut-off the trend is more useful than the number.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: September 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
