Waist-to-height ratio: keep your waist under half your height
Here is a health check you can do in a minute with a tape measure. Measure your waist. Measure your height. Divide the first by the second.
waist-to-height ratio = waist ÷ height
Use the same unit for both, centimetres or inches. If you are 170 cm tall and your waist is 85 cm, your ratio is 0.5.
The rule: under half your height
In 2005, the researchers Ashwell and Hsieh put the message in one line:
Keep your waist circumference to less than half your height.
That is a ratio under 0.5. A review in 2010 looked at 34 analyses that linked the ratio to diabetes, heart disease and related risks. The boundary values they suggested averaged 0.50, for men and for women.
NICE, the National Institute for Health and Care Excellence in England, now uses the ratio in its 2025 obesity guideline. It sorts adults into three bands:
| Ratio | NICE band |
|---|---|
| 0.4 to 0.49 | Healthy central adiposity, no increased health risks |
| 0.5 to 0.59 | Increased central adiposity, increased health risks |
| 0.6 or more | High central adiposity, further increased health risks |
“Central adiposity” means fat around your middle. NICE says the bands apply to adults of both sexes and all ethnicities with a BMI under 35, including people with a lot of muscle.
Why your waist says more than BMI
BMI only knows your weight and height. It cannot tell muscle from fat, or where your fat sits. Your waist size reflects the fat around your middle. NICE asks doctors to measure the ratio, as well as BMI, for adults with a BMI under 35.
How to measure your waist
NICE gives these steps for measuring yourself:
- Find the bottom of your ribs and the top of your hips.
- Wrap the tape around your waist midway between those two points. For most people that is just above the belly button.
- Breathe out naturally, then read the tape.
Measure your height without shoes. If you know your height in feet and inches, convert it all to inches first. For example, 5 feet 7 inches is 67 inches.
What the numbers look like
| Height | Waist for a ratio of 0.5 | Waist for a ratio of 0.6 |
|---|---|---|
| 155 cm | 77.5 cm | 93 cm |
| 165 cm | 82.5 cm | 99 cm |
| 175 cm | 87.5 cm | 105 cm |
| 185 cm | 92.5 cm | 111 cm |
Treat 0.5 as a boundary, not a cliff
Risk rises gradually as the ratio rises. It does not jump at 0.5. The authors of the 2010 review chose the words “boundary values” on purpose, because the values sit inside a continuous relationship. A ratio of 0.51 is not much worse than 0.49. A ratio that falls from 0.58 to 0.52 over a year is real progress, even if it never drops below 0.5.
Measure every few weeks, the same way each time, and follow the direction. Downtrend keeps your waist measurements and shows your ratio on a scale with the 0.5 line, with your previous measurement beside it. Together with your trend weight, it tells you whether the weight you lose is coming off your middle.
Sources
- Ashwell M, Hsieh SD. Six reasons why the waist-to-height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. International Journal of Food Sciences and Nutrition, 2005.
- Browning LM, Hsieh SD, Ashwell M. A systematic review of waist-to-height ratio as a screening tool for the prediction of cardiovascular disease and diabetes: 0.5 could be a suitable global boundary value. Nutrition Research Reviews, 2010.
- NICE. Overweight and obesity management, guideline NG246, 2025. Recommendations 1.9.5, 1.9.8, 1.9.14 and box 1.
This article is general information, not medical advice. Talk to a doctor before a big change to what you eat or how you train, and especially if you are pregnant, under 18 or have a health condition.