What this calculator does
Find your waist-to-height ratio and see how it compares with a widely used guideline. The waist-to-height ratio (WHtR) is your waist measurement divided by your height. It's one of the simplest body measures there is: one tape measurement, one height and a division. Researchers find it useful because it reflects fat carried around the belly. It also allows for the fact that taller people naturally have bigger waists.
This calculator gives your ratio and compares it with the widely cited guideline of 0.5. That's often put as "keep your waist to less than half your height." A ratio of 0.5 or more is a screening sign, a flag that may be worth talking over with a healthcare professional. It isn't a diagnosis, and a lower ratio doesn't rule anything out.
Where it's used
Why this math matters outside the classroom:
- Finding the ratio. A 34-inch waist and a 70-inch height give a ratio of 34 ÷ 70, which is about 0.49.
- Half your height. The 0.5 guideline is another way of saying the waist is less than half the height, a ratio of 1 to 2.
- Units cancel. Because both lengths share a unit, 86 cm ÷ 178 cm and 34 in ÷ 70 in give nearly the same ratio.
- Tracking over time. People measure their waist each month and log the ratio to see a trend rather than a single reading.
- Population surveys. Public health researchers record the ratio in large surveys because it needs nothing more than a tape measure.
Grade level and standards: Grade 6; Common Core State Standards for Mathematics 6.RP.A.1. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Choose US units (feet and inches) or metric (centimeters).
- Enter your height without shoes.
- Enter your waist measurement in the same units.
- Read your ratio and how it compares with 0.5. You'll also see the waist size that would equal exactly half your height.
What the inputs mean
- Height (feet)
- Stand straight against a wall without shoes. You can enter part of an inch in the inches box.
- Waist circumference
- A common way is to place the tape halfway between the bottom of your lowest rib and the top of your hip bone. Measure after a normal breath out. If you're tracking changes, measure the same way every time.
Formula and method
WHtR = waist circumference ÷ height (same unit) Guideline: WHtR below 0.5, i.e. waist < height ÷ 2
WHtR is the waist-to-height ratio, and waist circumference is the distance around your waist. The waist and height must be in the same unit. For US units, the calculator first turns feet and inches into total inches. The units cancel out, so the ratio is a plain number. It comes out the same whether you measure in inches or centimeters.
The ratio is rounded to two decimals before it's compared with 0.5, so 0.495 counts as 0.50. Turning the guideline around gives the waist size where the ratio would be exactly 0.5: half your height.
Worked example
Someone is 5 ft 7 in tall and measures a 32-inch waist.
- Height in inches: 5 × 12 + 7 = 67 in.
- Ratio: 32 ÷ 67 = 0.4776, which rounds to 0.48.
- 0.48 is below 0.5. The waist that would give exactly 0.5 is 67 × 0.5 = 33.5 in.
Result: The waist-to-height ratio is 0.48, below the 0.5 guideline. A 33.5-inch waist would reach it.
Understanding the result
The 0.5 line is popular because it's the same for everyone and easy to remember. Take a piece of string as long as your height and fold it in half. If your ratio is below 0.5, it should fit around your waist.
Some guidance adds a higher band above 0.5 for a further rise in risk. Some research suggests different lines for children or particular groups. This calculator reports only the 0.5 guideline.
A ratio of 0.5 or more is a reason to talk with a doctor or nurse, not a conclusion. They can weigh it alongside blood pressure, blood tests, activity and family history.
Assumptions and limitations
- The person is an adult and not pregnant.
- Waist and height are measured accurately, in the same unit system.
- A tape measurement can change by an inch or more depending on where you place it and how you breathe. For someone 5 ft 7 in tall, that shifts the ratio by about 0.015.
- The ratio doesn't measure body fat percentage, fitness or any specific condition, and it can't diagnose anything.
- A single line can't reflect differences in build, age or ethnicity.
Frequently asked questions
What does "keep your waist to less than half your height" mean?
It's the 0.5 guideline in plain words. If you're 170 cm tall, a waist under 85 cm gives a ratio below 0.5. The calculator shows that half-height waist size for you.
Why use waist-to-height rather than waist alone?
A fixed waist limit treats a short person and a tall person the same. But taller people naturally have bigger waists. Dividing by height adjusts for that.
How is this different from the waist-to-hip ratio?
The waist-to-hip ratio compares your waist with your hips. It uses different cut-offs for men and women. The waist-to-height ratio compares your waist with your height. It usually has a single line of 0.5 for adults.
Can I use it during pregnancy?
No. The waist grows naturally during pregnancy, so the ratio doesn't mean the same thing.
How this calculator is checked
Method: Waist circumference ÷ height; the 0.5 boundary is the widely cited adult screening guideline ("waist less than half your height"). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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