Optional – needed for WHR, WHtR, and body fat (Navy method)
Primary indices
Ideal weight
Body fat estimate
How to use the Body Indices Calculator
- Choose metric or imperial units and your biological sex.
- Enter your age, weight, and height, the main indices are calculated automatically.
- Add waist, hip, and neck measurements to get WHR, WHtR, and body fat estimates.
Understanding each index
- BMI (Body Mass Index): weight / height². Simple and widely used, but does not account for muscle mass, body composition, or fat distribution.
- Ponderal Index (Corpulence Index): weight / height³. More accurate than BMI for very tall or very short people because it scales with height cubed rather than squared.
- WHR (Waist-to-Hip Ratio): waist circumference ÷ hip circumference. Risk threshold: >0.90 (men), >0.85 (women). Abdominal obesity is a stronger predictor of cardiovascular risk than overall weight.
- WHtR (Waist-to-Height Ratio): waist circumference ÷ height. A value above 0.5 indicates elevated cardiovascular risk. Considered a better predictor than BMI alone.
- Navy Method (body fat): uses circumference measurements to estimate body fat percentage. Accuracy ±3-4% compared to DEXA scan.
- BMI Method (body fat): estimates body fat from BMI, age, and sex using regression formulas. Less accurate than the Navy method.
Waist circumference thresholds vary significantly by region, and by organisation
This is where most body composition calculators get it wrong. The threshold for "increased risk" based on waist circumference is NOT the same worldwide:
| Population | Guideline | Men (increased risk) | Women (increased risk) |
|---|---|---|---|
| Europeans (UK, France, Germany, Spain, Portugal) | IDF 2006 | ≥ 94 cm | ≥ 80 cm |
| USA / Canada | AHA/NHLBI | ≥ 102 cm | ≥ 88 cm |
| South Asians (India, Pakistan...) | IDF Asian | ≥ 90 cm | ≥ 80 cm |
| East Asians (China, Japan, Korea) | IDF Asian | ≥ 90 cm | ≥ 80 cm |
A European man with a 96 cm waist is at "increased risk" (IDF Europe). The same man would be classified as "normal" under the US AHA criteria (below 102 cm). This discrepancy explains why European health authorities often flag more people as at risk than their US counterparts, not because Europeans are unhealthier, but because the European thresholds are set at a lower absolute level.
WHtR, the emerging gold standard
Research increasingly shows that Waist-to-Height Ratio (WHtR) is a better predictor of cardiovascular risk than BMI or waist circumference alone. The "keep your waist to less than half your height" rule is simple and universal, it corrects for height automatically, unlike waist circumference alone. A 180 cm man and a 160 cm woman have different absolute waist thresholds, but the 0.5 WHtR threshold applies to both.
Reference ranges
| Index | Healthy range | At-risk threshold |
|---|---|---|
| BMI | 18.5-24.9 | ≥ 25 overweight (European); ≥ 23 Asian-adjusted |
| WHR (men) | < 0.90 | ≥ 0.90 (IDF/WHO) |
| WHR (women) | < 0.85 | ≥ 0.85 (IDF/WHO) |
| WHtR | < 0.50 | ≥ 0.50, regardless of gender or ethnicity |
| Body fat % (men) | 10-20% (fit) | > 25% obese |
| Body fat % (women) | 20-30% (fit) | > 35% obese |
IDF 2006 waist thresholds; AHA/NHLBI from ATP III; WHO recommendations. Consult a healthcare provider for personalised assessment.