Waist-to-Height Ratio Calculator

Divide your waist by your height to check central adiposity against the NICE NG246 bands, and see the waist size that keeps you under the 0.5 line.

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Keep your waist to less than half your height

The waist-to-height ratio is your waist circumference divided by your height, measured in the same units. Because it is a ratio, inches and centimeters give the same answer. A 5 ft 9 in (69-inch) adult with a 34-inch waist has a ratio of 34 ÷ 69 = 0.49.

The NICE bands. The UK National Institute for Health and Care Excellence adopted the ratio in its 2025 overweight and obesity guideline, NG246:

  • 0.40 to 0.49: healthy central adiposity, no increased health risk
  • 0.50 to 0.59: increased central adiposity, increased health risk
  • 0.60 or more: high central adiposity, further increased health risk

NICE's plain-language message is to keep your waist to less than half your height. For that 69-inch adult, the line sits at 34.5 inches; for someone 175 cm tall, it is 87.5 cm. The calculator shows your personal line and how far above or below it you are.

Who the bands apply to. NICE says the ratio can be used for adults with a BMI under 35 of any sex and any ethnicity, including people with high muscle mass. Above a BMI of 35, NICE considers the health risk high regardless, so the ratio adds little. It does not apply during pregnancy. Values below 0.40 are not classified by NICE; a very low ratio may simply reflect a slim build but is worth mentioning to a clinician if weight is also low.

Why waist-to-height beats BMI and waist size alone

Fat stored around the abdomen, especially visceral fat around the organs, is more strongly linked with type 2 diabetes, high blood pressure and heart disease than fat stored elsewhere. BMI cannot see where fat sits, and a raw waist measurement ignores body size: a 36-inch waist means something different on a 6 ft 4 in man than on a 5 ft 2 in woman.

A 2012 systematic review and meta-analysis by Ashwell, Gunn and Gibson pooled 31 studies covering more than 300,000 adults from several ethnic groups. Waist-to-height ratio discriminated cardiometabolic risk significantly better than BMI, and better than waist circumference for diabetes, hypertension and cardiovascular outcomes in both men and women. A single 0.5 boundary working across sexes and ethnicities is a large part of its appeal.

Measuring correctly. NICE describes the waist as the midpoint between the lowest rib and the top of the hip bone (iliac crest). Stand, breathe out normally, and keep the tape level and snug without compressing the skin. Measuring at a different spot, such as the navel, can give a noticeably different reading, so use the same landmark every time.

Using the result. Because height is fixed in adulthood, the ratio only moves when your waist does. Each inch lost from the waist lowers the ratio by roughly 0.014 for someone 70 inches tall. Re-measure every few weeks at the same time of day, since meals and bloating change the reading.

Common Measuring Mistakes

The ratio is only as good as the tape measurement behind it, and small errors matter because the bands are just 0.10 wide.

  • Using your trouser size. Jeans sit below the waist, and sizes vary between brands. Measure with a tape instead.
  • Measuring at the wrong landmark. Find the midpoint between your lowest rib and the top of your hip bone. Measuring at the navel or at the narrowest point changes the result.
  • Holding your breath or pulling in your stomach. Stand relaxed and measure after a normal breath out.
  • Letting the tape tilt. A tape that dips at the back reads larger. Use a mirror or ask someone to check that it is level all the way around.
  • Mixing units. Waist in centimeters divided by height in inches gives a meaningless number. Use the same unit for both, or let the calculator convert.
  • Using out-of-date height. Adults lose height with age, so measure it rather than relying on an old driver's license figure.
  • Reading one measurement as a trend. Waist size changes through the day with meals and bloating. Measure at the same time, ideally in the morning, and compare over weeks.

Frequently Asked Questions

Common questions about the Waist-to-Height Ratio Calculator

NICE guideline NG246 classes 0.40 to 0.49 as healthy central adiposity. A ratio of 0.50 to 0.59 means increased health risk, and 0.60 or more means further increased risk.

Sources & References

NICE NG246: Overweight and obesity management - Identifying and assessing overweight, obesity and central adiposity

Defines the waist-to-height ratio bands (0.40-0.49 healthy, 0.50-0.59 increased, 0.60+ high), who they apply to and how to measure the waist.
→Source: National Institute for Health and Care Excellence (NICE)

Ashwell M, Gunn P, Gibson S. Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors. Obes Rev. 2012;13(3):275-286

Meta-analysis of 31 studies (300,000+ adults) showing waist-to-height ratio outperforms BMI and waist circumference for cardiometabolic risk.
→Source: Obesity Reviews (PubMed)

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