Waist-to-Height Ratio Calculator
This waist-to-height ratio calculator checks whether your waist is less than half your height.
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Field Notes that go deeper
The science behind the waist-to-height ratio calculator
Show the formulas, method and sources
The waist-to-height ratio divides your waist by your height. A simple screening message says to keep your waist to less than half your height, which is a ratio of 0.5. The tool shows your ratio and how far your waist sits from half your height.
Formulas
Ratio
Waist-to-height ratio = waist circumference / height (same units)
Half-height waist
Half-height waist = 0.5 x heightBoundary used: 0.5 (at or above)
How it works, step by step
- First, the calculator converts your waist and height to centimeters.
- Then it divides the waist by your height.
- Finally, it compares the ratio with 0.5 and shows the waist length that matches half your height.
Worked example
A person who is 180 cm tall with a 100 cm waist has a ratio of 100 / 180 = 0.56. Half of their height is 90 cm, so their waist is 10 cm above that.
Accuracy and limits
Ashwell and Gibson call 0.5 a widely used boundary. It also becomes one simple message: keep your waist to less than half your height.
They also lean on a systematic review of 78 studies, which reported that the 0.5 boundary looked appropriate across adult ages, sexes and ethnic groups.
Because the paper gives no detailed measuring protocol, the tool borrows a waist method from a 2024 study. It measures at the midpoint between the lower rib and the top of the hip bone.
- One boundary for all adults cannot describe small differences between people.
- The evidence covers adults, so this calculator is for adults.
- It is a screening ratio, so a clinician can read it alongside your other health information.
Sources
- Ashwell M, Gibson S. A proposal for a primary screening tool: 'Keep your waist circumference to less than half your height'. BMC Med. 2014;12:207. Used for: The 0.5 waist-to-height boundary and the evidence behind it.
- Assefa M, Tsegaye A, Addissie A, Worku A. Body composition-derived abdominal circumference, waist-to-hip ratio, and waist-to-height ratio cut-offs for Ethiopian adults in Northwest Ethiopia, 2023. J Health Popul Nutr. 2024;43:185. Used for: The WHO waist-hip ratio cut-offs as quoted, and how waist and hip were measured.
Sources and math last reviewed: .
Questions people ask
What is the waist-to-height ratio?
It is your waist divided by your height. If your waist is exactly half your height, the ratio is 0.5.
What does keeping your waist under half your height mean?
It is a simple screening message built on the 0.5 boundary. Ashwell and Gibson describe a string measuring half your height, which should fit around your waist if your ratio is under 0.5.
How do I measure my waist?
Stand relaxed and use a flexible tape. Measure at the midpoint between the lowest rib and the top of the hip bone, then breathe out and read the tape.
What is the difference between this and BMI?
BMI compares weight with height and ignores where weight sits. The waist-to-height ratio focuses on your middle, so the two can point in different directions.
What should I do if my ratio is 0.5 or higher?
If your ratio is 0.5 or higher, treat it as a prompt to look at the whole picture. A clinician can read it with your blood tests, your habits and how you feel.
How do I find half my height?
Divide your height by two. At 170 cm tall, half of your height is 85 cm, so a waist under 85 cm gives a ratio under 0.5.
These calculators give general estimates for adults and are not medical advice. For decisions about your own health, talk with a doctor or a registered dietitian. How we write and check things