Where fat sits matters as much as how much of it there is. The waist-to-hip ratio is a two-measurement test for central (abdominal) fat — the pattern most associated with metabolic risk — and it catches what BMI structurally cannot.
The WHO categories
World Health Organization guidance flags substantially increased risk above 0.90 for men and 0.85 for women. This calculator maps your ratio onto those sex-specific bands — the colored scale shifts when you toggle sex, because the cutoffs do.
Measuring correctly (most errors happen here)
Waist: find the midpoint between your lowest rib and the top of the hip bone — usually just above the navel — and measure after a normal exhale, tape snug but not digging in. Hips: the widest point around the buttocks. Stand relaxed, feet together, tape parallel to the floor. Morning measurements before eating are the most repeatable.
Why central fat is the signal
Visceral fat — packed around abdominal organs — is more metabolically active and harmful than subcutaneous fat on hips and thighs. Two people with identical BMI can carry opposite risk profiles depending on this distribution; "apple vs pear" is the folk version of the same observation. That's also why normal-weight central obesity (healthy BMI, elevated WHR) is worth catching.
Use it alongside, not instead of
WHR is one lens. Pair it with BMI for overall mass, the body fat calculator for composition, and waist circumference alone (WHO flags 94+ cm for men, 80+ cm for women) as a companion signal. Trends over months beat any single reading.
Screening guidance from WHO cutoffs; not a diagnosis — discuss results with a clinician.