How to Use This Tool
Enter your waist and hip measurements in either unit. The ratio is unit-free — 35 by 40 inches and 88.9 by 101.6 centimetres both give 0.875 — so use whichever tape you own, just not one of each.
Where to put the tape
This matters more than anything else on this page, because the measurement error is larger than the differences the ratio is meant to detect.
- Waist: the WHO site is the midpoint between the lowest rib and the top of the hip bone (the iliac crest), measured at the end of a normal breath out. This is usually above the navel, and measuring at the navel instead typically reads several centimetres larger.
- Hip: the widest part of the buttocks, tape horizontal all the way round.
- Both: tape snug but not compressing the skin, standing relaxed, no held breath, and over bare skin or a single thin layer.
One centimetre of waist changes the ratio by about 0.010, and one centimetre of hip by about 0.009. A risk category is roughly 0.05 wide. So five centimetres of inconsistent tape placement — easily the gap between the WHO site and the navel — moves a person across a whole category without their body changing at all.
The practical implication: a single reading is close to meaningless, and comparing your reading to someone else's is worse. Measure the same way each time and watch the trend.
What the cut-offs are
The WHO expert consultation defines substantially increased risk of metabolic complications at a ratio of 0.90 or above for men and 0.85 or above for women. Those numbers come from population studies of cardiometabolic outcomes, and they are population thresholds — a statement about groups, not a diagnosis of an individual.
Why a ratio can be misleading
Dividing by hip circumference is the point — it is what makes this a measure of fat distribution rather than fat quantity, and abdominal fat is more strongly associated with metabolic risk than fat carried on the hips and thighs.
It is also the weakness. Large hips shrink the ratio regardless of what the waist is doing. A waist of 100 cm with hips of 118 cm gives 0.847, under the male threshold — while that same 100 cm waist is already past the WHO increased-risk waist circumference of 94 cm for men. The ratio says fine; the waist says otherwise.
That is why waist circumference is shown here as its own number. WHO increased-risk waist marks are about 94 cm for men and 80 cm for women, with substantially increased risk around 102 cm and 88 cm. Some health bodies use lower thresholds for South Asian, Chinese and Japanese populations, because metabolic risk appears at smaller waist sizes.
What this cannot tell you
It is a tape measure and a division. It knows nothing about your blood pressure, blood glucose, lipids, fitness, medication, or family history, and any of those changes the picture more than the ratio does. Muscle, pregnancy, recent weight change and bloating all move the numbers without meaning what the thresholds assume they mean.
Use it as one input among several, and take anything that concerns you to a doctor rather than to a calculator. This is general information, not medical advice.
