UNDERSTAND THE METHOD
Measure the correct site
For this ratio, follow the National Institute for Health and Care Excellence method: find the bottom of your ribs and the top of your hips, then place the tape midway between them. Let the tape stay level around your waist. Breathe out naturally before reading it. This site can differ from the site used by a body-fat equation. Record the site with the number so a later reading uses the same procedure.
Calculate the ratio
Divide waist circumference by height in the same units. For example, 85 cm divided by 170 cm is 0.50. Inches work in the same way if both measurements use inches. A ratio has no unit. Check the entered units before comparing two records. A 1 cm change in waist at 170 cm changes the ratio by about 0.006; this is arithmetic sensitivity, not a change in health status by itself.
Understand the guideline
The guideline uses waist-to-height ratio to assess central adiposity in adults with body mass index below 35. It describes 0.5 to 0.59 as increased central adiposity and 0.6 or higher as high central adiposity. These are screening categories. They are not a diagnosis, and they do not describe all health factors. The guideline directs people with an increased-risk result to seek further assessment from a health professional.
Pair it with the right context
This ratio describes waist size relative to height. It does not estimate a body-fat percentage, visceral-fat area, or the amount of fat in kilograms. If you also use the body-fat calculator, keep the two results separate. A change in tape position can change the ratio, so repeated readings need the same site and relaxed breathing. Save the date, raw waist value, height, and measurement procedure.
Common questions
Is 0.50 a body-fat percentage?
No. It is waist divided by height. It does not measure body-fat percentage.
Can I mix centimeters and inches?
No. Convert both measurements to the same unit before dividing.
Why does this waist site differ from a Navy tape estimate?
The two methods define their own measurement sites. Follow the instructions for the result you want.
Sources & limitations
Sources checked September 12, 2026. These notes explain published methods. They have not received an independent clinical review.
- NICE gives the midpoint rib-to-hip waist method, ratio formula, scope for adults with BMI below 35, and interpretation categories.nice.org.uk
- BMI and other screening measures do not alone provide a full individual health assessment.cdc.gov
- The Navy body-composition method specifies its own natural-waist and other circumference sites.mynavyhr.navy.mil