Waist-to-height ratio is your waist measurement divided by your height, in the same units. Below 0.5 is healthy, 0.5 to 0.59 means increased health risk, and 0.6 or more high risk. In plain words: keep your waist to less than half your height. At 5 ft 9 in (69 inches), that means a waist under 34.5 inches.
The UK's NICE has recommended it alongside BMI since 2022, because it measures fat around the middle — the kind that drives type 2 diabetes and heart disease — and one cut-off works for men and women of every height and background.
Worked example
Height: 5 ft 9 inWaist: 36 inSex: Male
Waist-to-height ratio: 0.52 Increased health risk
At 5 ft 9 in, half your height is 34.5 inches, so a 36-inch waist is a ratio of 0.52 — just into the increased-risk band. Taking 1.5 inches off the waist would bring it down to the 0.5 line.
Open this example in the calculator →How to use the Waist-to-Height Ratio Calculator
- Choose US or metric units and enter your height.
- Measure your waist midway between your lowest rib and the top of your hip bone, relaxed, after breathing out.
- Optionally choose your sex to add the WHO waist thresholds and a body-fat estimate.
- Read your ratio, its band and the waist to aim for at your height.
Waist-to-height ratio chart
| Ratio | What it means | Waist at 5 ft 4 in | Waist at 5 ft 10 in |
|---|---|---|---|
| Below 0.4 | Low — check BMI too | under 25.6 in | under 28 in |
| 0.4–0.49 | Healthy | 25.6 to 31.9 in | 28 to 34.9 in |
| 0.5–0.59 | Increased risk | 32 to 38.3 in | 35 to 41.9 in |
| 0.6 or more | High risk | 38.4 in or more | 42 in or more |
Why it works better than BMI on its own
BMI cannot see where weight sits. Fat stored around the abdomen and organs (visceral fat) is the kind most strongly linked with insulin resistance, type 2 diabetes, high blood pressure and heart disease, and the waist tracks it directly. Dividing by height adjusts for body size, so a single boundary works for tall and short people — unlike a fixed waist size, which is too strict for a tall person and too lenient for a short one. In studies comparing the measures, waist-to-height ratio predicts cardiometabolic risk at least as well as BMI or waist alone, and better than BMI for many outcomes.
How to measure your waist
- Find the bottom of your lowest rib and the top of your hip bone. Measure midway between them — for most people, just above the belly button.
- Stand up straight, breathe out normally, and don’t pull your stomach in.
- Keep the tape level and snug, not tight. Measure twice.
- Your trouser size is not your waist: trousers usually sit lower and are often a few inches smaller.
Waist-to-height ratio for children
The same 0.5 boundary is used as a guide for children aged 5 and over, and NICE suggests it can help in assessing children and young people, whose BMI is otherwise read by percentile. A child’s waist growing faster than their height is a useful early sign to discuss with a doctor.
What if my ratio is high but my BMI is healthy?
That combination — sometimes called "normal-weight central obesity" — carries more risk than a healthy BMI suggests, and it is common, especially in South Asian adults and after menopause. Physical activity reduces visceral fat even before the scale moves much. For a fuller picture, try the body fat calculator.
Frequently asked questions
What is a good waist-to-height ratio?
Below 0.5 — a waist under half your height. NICE classes 0.4 to 0.49 as healthy, 0.5 to 0.59 as increased health risk and 0.6 or more as high risk.
How do I calculate waist-to-height ratio?
Divide your waist by your height, both in the same units. A 32-inch waist at 5 ft 6 in (66 inches) is 32 ÷ 66 = 0.48.
Is waist-to-height ratio better than BMI?
It measures something BMI misses — fat around the middle — and predicts heart disease and diabetes risk at least as well. Most guidelines now suggest using both: BMI for overall size, waist-to-height for where the fat is.
Is the 0.5 rule the same for men and women?
Yes. One of the strengths of the ratio is that a single boundary works for men and women, adults and children over 5, and people of different ethnic backgrounds.
What waist size should I have for my height?
Less than half your height: under 32 inches at 5 ft 4 in, under 34.5 inches at 5 ft 9 in, and under 36 inches at 6 ft. In centimeters, under 85 cm at 170 cm.
How can I reduce my waist-to-height ratio?
By reducing abdominal fat: regular physical activity (even without weight loss), fewer refined carbohydrates and sugary drinks, less alcohol and enough sleep. Waist size often falls faster than weight.
Sources
- Overweight and obesity management (NG246), 2025 — National Institute for Health and Care Excellence (UK)
- Ashwell M, Gibson S. Waist-to-height ratio as an indicator of “early health risk”. BMJ Open 2016;6:e010159 — BMJ Open
- Waist circumference and waist–hip ratio: report of a WHO expert consultation — World Health Organization
- Woolcott OO, Bergman RN. Relative fat mass (RFM) as a new estimator of whole-body fat percentage. Sci Rep 2018;8:10980 — Scientific Reports
- Thomas DM et al. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity 2013;21:2264–2271 — Obesity
- Rubino F et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol 2025;13:221–262 — The Lancet Diabetes & Endocrinology
For general information only — not a diagnosis or a substitute for advice from a doctor. How we calculate.