Calculate your waist-to-height ratio (WHtR) — a better predictor of metabolic risk than BMI. Shows risk category, half-circle gauge, and the 'keep it under 0.5' rule.
WHtR = Waist circumference ÷ Height (both in the same unit — cm or inches).
Risk thresholds (Ashwell & Gibson, British Journal of Nutrition): Under 0.4 = Extremely lean (potential underweight concern). 0.4–0.5 = Healthy. 0.5–0.6 = Overweight/increased risk. Over 0.6 = High risk (substantially increased metabolic and cardiovascular risk). These thresholds apply to adults of any sex and are largely ethnicity-independent, though South Asian populations tend to carry higher metabolic risk at the same WHtR, so some clinicians use a 0.45 threshold for South Asian adults.
Worked example: waist 85cm, height 170cm → WHtR = 85 ÷ 170 = 0.50. This sits exactly on the "healthy/overweight" boundary. A 5cm waist reduction (80cm) would give 0.47 — comfortably in the healthy range. A 175cm person would need a waist under 87.5cm to achieve the same 0.5 threshold.