How to measure your waist and hips
Stand relaxed and breathe out normally, keeping the tape snug and level but not digging in. The WHO method places the waist halfway between your lowest rib and the top of your hip bone. Measure your hips around the widest part of your buttocks. Enter both in centimeters; to convert, multiply inches by 2.54. Choose your sex, since the cut-off differs.
How the ratio is worked out
The ratio is simply waist divided by hip, rounded to two decimals. A WHO expert report gives a cut-off for substantially increased risk of metabolic complications at 0.90 or higher for men and 0.85 or higher for women. The tool compares the rounded number you see with that cut-off, so a result that displays as 0.90 counts as reaching it. Small errors matter: with 100 cm hips, 1 cm on the waist moves the ratio by 0.01.
Worked examples for a woman and a man
A woman with a 79 cm waist and 98 cm hips has a ratio of 79 ÷ 98 = 0.81, below the 0.85 cut-off. A man with a 94 cm waist and 100 cm hips has a ratio of 0.94, above the 0.90 cut-off, so the result reads substantially increased risk.
What the ratio tells you
This measure looks at where fat sits rather than how much you weigh. Health Canada explains that fat around the waist and upper body carries more health risk than fat around the hips and thighs, the familiar apple and pear shapes.
A result above the cut-off is a prompt to look further, not a verdict on your health. A result below it is not a guarantee either.
Limits of the waist-to-hip ratio
The WHO report found that higher waist measures are linked to higher disease risk, but most of its data came from people of European descent, and it reports ethnic differences in fat distribution. It also notes that hips are harder to measure than the waist and favored waist size for ease of use.
The ratio does not suit children or pregnancy, and because it divides two numbers, it can stay flat when both change together.