Waist-to-Height Ratio & Body Roundness Index
Is your waist less than half your height? Plus Body Roundness Index and ABSI.
Enter your waist and height.
NICE bands: 0.4–0.49 healthy · 0.5–0.59 increased · 0.6 or more high (scale 0.3–0.8)
Body Roundness Index in context
| US adults (NHANES) | Men | Women |
|---|
Average BRI by BMI group, Thomas et al., Table 3. In a later study of 32,995 US adults (Zhang et al.), death from any cause was more likely with a BRI below 3.4 or of 6.9 and above than with a BRI of 4.5–5.5.
How it was calculated
For general information only, not medical advice. Consult a qualified health professional for advice about your situation.
About the Waist-to-Height Ratio & Body Roundness Index
The waist-to-height ratio is your waist circumference divided by your height. It is the measure the UK’s NICE recommends for central adiposity — fat stored around the middle — with one simple message: keep your waist to less than half your height.
This calculator gives your ratio and its NICE band, and the waist you would need to stay below 0.5. Add your weight, sex and age to see two newer shape indices as well: the Body Roundness Index (BRI), which models the body as an ellipse to estimate how round it is, and A Body Shape Index (ABSI), which shows whether your waist is larger or smaller than expected for your height and weight. Each comes with plain-language notes on what it can and cannot tell you.
How to use it
- Measure your height without shoes, and your waist midway between the bottom of your ribs and the top of your hips — just above the belly button — after breathing out naturally.
- Enter both, in centimetres or in feet and inches. The ratio is the same in any unit.
- Optionally add your sex, age and weight for the Body Roundness Index, A Body Shape Index and its z-score.
- Read your ratio and band, the waist that would keep you under 0.5, and the notes. Use Copy result to keep a record.
Examples
Ratio 0.57 — increased central adiposity · keep the waist under 85 cm · BRI 4.72
Ratio 0.57 — the same as in centimetres
Ratio 0.48 — healthy central adiposity · BRI 3.03 · ABSI 0.0766, z-score −1.16 (waist smaller than average for his height and weight)
NICE bands
NICE guideline NG246 classifies central adiposity by waist-to-height ratio for adults with a BMI under 35 — men and women of all ethnicities, including people with high muscle mass — and for children and young people aged 5 and over (recommendation 1.10.10):
- 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
The risks NICE names are type 2 diabetes, high blood pressure and cardiovascular disease. Its worked example: 96.5 cm ÷ 170 cm = 0.57, or 38 in ÷ 67 in = 0.57.
Why waist-to-height?
Waist size says more than BMI about fat around the organs, and dividing by height makes one boundary work for short and tall people. A systematic review and meta-analysis by Ashwell, Gunn and Gibson — 31 studies of more than 300,000 adults in several ethnic groups — found the waist-to-height ratio discriminated better than BMI for adult cardiometabolic risk factors, and better than waist circumference for diabetes, high blood pressure, cardiovascular disease and all outcomes combined, in men and women.
Body Roundness Index (BRI)
Thomas et al. treated the body as an ellipse whose long axis is your height and whose width comes from your waist: BRI = 364.2 − 365.5 × √(1 − (waist ÷ 2π)² ÷ (0.5 × height)²), with waist and height in the same unit. In their NHANES data it ranged from 1.0 (very narrow) to about 18 (very round), and the average was 3.07 for men and 3.28 for women with a healthy BMI, and 6.47 and 6.86 at a BMI of 30–39.9. BRI predicted body-fat and visceral-fat percentages slightly better than BMI or waist alone.
There are no official BRI cut-offs. In a study of 32,995 US adults, Zhang et al. found a U-shaped link with death from any cause: risk was 25% higher with a BRI below 3.4 and 49% higher at 6.9 or more, compared with a BRI of 4.5–5.5. That describes a population, not you.
A Body Shape Index (ABSI)
Krakauer and Krakauer built ABSI = waist ÷ (BMI^(2/3) × height^(1/2)), with waist and height in metres, so that it barely depends on height, weight or BMI — it isolates the part of your waist size that BMI does not explain. Typical adult values are around 0.08. Because ABSI rises with age and differs between men and women, the calculator also gives a z-score against the US NHANES 1999–2004 average and standard deviation for your age and sex. In that population death rates rose with above-average ABSI (about 33% per standard deviation), across ages, both sexes and white and black participants — but not in Mexican Americans.
What these numbers can and cannot tell you
- They can flag fat stored around your middle, which BMI misses, and they are free, quick and repeatable.
- They cannot diagnose anything or measure visceral fat directly — that needs imaging.
- NICE’s bands are guideline thresholds; BRI and ABSI have none. Their risk links come from US population studies and may not transfer to every group.
- Tracking your own waist over time, measured the same way, is often more useful than any single number.
Sources
- NICE. NG246 Overweight and obesity management — recommendations 1.9.5, 1.9.14, 1.9.15, 1.10.10 and box 1
- 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 13:275-86
- Thomas DM et al. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity 21:2264-71 — formula and Table 3
- Zhang X et al. Body Roundness Index and all-cause mortality among US adults. JAMA Netw Open 7:e2415051 (formula as corrected in the published erratum)
- Krakauer NY, Krakauer JC. A new body shape index predicts mortality hazard independently of body mass index. PLoS One 7:e39504 — formula and Table S1
Limitations
- Screening measures only: they do not diagnose any condition.
- NICE’s bands are for adults with a BMI under 35 and for children and young people aged 5 and over; BRI and ABSI are shown for adults only.
- ABSI z-scores compare you with US adults measured in 1999–2004; populations differ.
- Heights of 80–250 cm, waists of 30–250 cm and weights of 10–300 kg are accepted.
Privacy
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Frequently asked questions
What is a healthy waist-to-height ratio?
NICE calls 0.4 to 0.49 healthy. From 0.5 the health risks increase, and 0.6 or more is high. Put simply: keep your waist to less than half your height — under 85 cm if you are 170 cm tall.
Do I need different cut-offs for my sex or ethnicity?
No — that is one of its advantages. NICE uses the same bands for men and women of all ethnicities, including people with high muscle mass, as long as the BMI is under 35.
Is the Body Roundness Index better than BMI?
In the original study it predicted body-fat and visceral-fat percentage slightly better than BMI, and a large US study has linked it to mortality. But it has no agreed healthy range, so use it alongside your waist-to-height ratio and BMI, not instead of them.
What does a positive ABSI z-score mean?
Your waist is larger than average for your height and weight compared with US adults of your age and sex in 1999–2004. A z-score of +1 is one standard deviation above that average. In that population higher ABSI went with higher death rates, but it is not a personal risk score.
Can I use this for my child?
For children and young people aged 5 and over, yes: NICE uses the same waist-to-height bands. BRI and ABSI were developed in adults, so they are not shown for under-18s. For BMI, use the child BMI percentile calculator.