The waist-to-hip ratio is one of the most widely used health calculations on the internet, and it has a flaw that almost no calculator mentions: a ratio cannot see how big you are.
Divide your waist by your hips and you get a number that describes your proportions. It tells you nothing at all about your actual waist measurement — and your actual waist measurement is the thing the evidence is strongest about. That is why the calculator above shows you both, and says so plainly when they disagree.
The thresholds, and who set them
The waist-to-hip figures come from the WHO Expert Consultation on Waist Circumference and Waist–Hip Ratio. At or above these numbers, WHO classes it as abdominal obesity — which is a screening category, not a diagnosis.
| Measure | Women | Men |
|---|---|---|
| Waist-to-hip ratio (WHO) | 0.85 or above | 0.90 or above |
| Waist — increased risk (WHO) | 80 cm / 31.5 in | 94 cm / 37 in |
| Waist — substantially increased risk (WHO) | 88 cm / 35 in | 102 cm / 40 in |
| Waist-to-height ratio (NICE NG246) | Under 0.5 healthy · 0.5–0.59 increased · 0.6+ high | |
Why a good ratio can hide a large waist
The ratio is waist divided by hips. Rearrange that and you get waist = ratio × hips — so the larger your hips, the more waist you can carry before the ratio says anything at all.
The crossover points are exact, not approximate. For women, at WHO’s 0.85 threshold:
Identical ratios, twenty centimetres of waist between them. A calculator that reports only the ratio gives both women the same answer.
Two exact numbers fall out of this, for women:
- Hips above 103.5 cm — a passing ratio permits a waist beyond 88 cm, which is WHO’s substantially-increased-risk line.
- Hips below 94.1 cm — the ratio flags you while your waist is still under 80 cm, which WHO treats as unremarkable.
How often does this matter? We swept 14,144 plausible waist and hip combinations for women. 21% produced a passing ratio while the waist sat in the substantially-increased-risk band, and 2.4% were flagged by the ratio while the waist was entirely healthy. For men it is 16.4% and 4.6%.
One in five wrongly reassured is not a rounding error. It is the reason this calculator reports your waist measurement alongside the ratio instead of the flattering number on its own.
The popular calculators disagree about men
Worth knowing if you have looked this up before and got a different answer. Among the highest-ranking waist-to-hip calculators, one puts men’s “low risk” at 0.95 or below, while WHO — and other calculators quoting WHO — put abdominal obesity at 0.90 or above.
So a man with a ratio of 0.92 is told he is at low risk by one page and that he meets the definition of abdominal obesity by another. More awkwardly, the calculator using 0.95 quotes the WHO 0.90 figure in its own body text on the same page — its table and its prose contradict each other.
We use WHO’s numbers throughout, for both sexes, and the top band begins exactly where WHO says it does.
How to measure properly
Most of the error in this calculation comes from the tape, not the arithmetic.
- Waist: midway between the bottom of your lowest rib and the top of your hip bone. That is WHO’s landmark. It is usually just above the navel, but find the bones — the navel moves.
- Hips: the widest part of your buttocks, tape level all the way round. Check the back in a mirror, because the tape slides down without you noticing.
- Breathe out normally. Do not hold it in. This is the easiest way to flatter yourself by three centimetres, and the person you are fooling is you.
- Snug, not tight. Do not compress the skin. Over clothes adds a centimetre or two.
- Same time of day. Ideally morning, before eating. A large meal genuinely changes a waist measurement.
One thing that trips up comparisons: different bodies of guidance use different waist landmarks. WHO uses the rib-to-hip midpoint; some large American surveys measure at the top of the hip bone instead. On the same person those can differ by several centimetres. If you are comparing today’s number against one from years ago, make sure both were taken in the same place.
Apple, pear, and what the shape actually means
A lower ratio is the pattern usually called pear-shaped: weight carried at the hips and thighs. A higher ratio is apple-shaped: weight around the middle.
The reasoning behind the measure is that where fat sits seems to matter independently of how much of it there is. Fat stored around the organs is more metabolically active than fat stored at the hips and thighs, which is why two people at the same weight can sit differently on a risk chart.
Two honest caveats. First, muscle counts as hips — someone with well-developed glutes has a lower ratio for reasons unconnected to abdominal fat, and the tape cannot tell the difference. Second, this is not the same question as the one our body shape calculator answers. That one sorts you into seven shapes for the purpose of buying clothes that fit. This one is about fat distribution and health screening. Related, but not interchangeable.
What changes after 50
This is where the ratio becomes genuinely misleading, and it is the part most calculators say nothing about.
Your ratio can rise without your waist changing at all
The hips are the denominator. Anything that makes them smaller pushes the ratio up — and glute and thigh muscle is lost steadily from midlife onward.
Three and a half centimetres of hip — muscle, not fat — is all it takes to cross WHO’s threshold with an unchanged waist. The calculator now flags her. Her abdomen is identical.
And menopause moves fat waist-ward at the same weight
Separately from any weight change, fat redistributes from the hips toward the waist after menopause. Shift three centimetres from hips to waist at identical body weight and the ratio moves by about 0.056 — most of the way across a category, with the scales reading exactly the same.
Both effects push in the same direction, and neither is what the ratio is trying to detect. This is why the waist measurement itself is the more stable thing to track after 50, and waist-to-height more stable still: losing three centimetres of height moves waist-to-height by less than 0.01.
There is a practical upshot. Resistance training that maintains glute and thigh muscle keeps the denominator up — which is a genuine reason to lift something heavy twice a week, and a considerably better one than the number on this page.
Where this measurement falls down
- It is not a diagnosis and cannot be. It knows nothing about your blood pressure, your blood sugar, your fitness, your family history or how you feel.
- Thresholds are lines drawn through continuous data. Nothing happens to you at 0.85 that did not happen at 0.84.
- It was built to sort populations, not to judge individuals. That is a real distinction and it gets lost constantly.
- Bloating, digestive conditions, some medications and abdominal surgery all move a waist measurement without moving anything about long-term risk.
- If numbers like these are unhelpful for you — and for some people they genuinely are — that is a perfectly good reason to close the tab. The measurement is not going anywhere.
Common questions
What is a good waist-to-hip ratio?
Below 0.85 for women and below 0.90 for men, per WHO. But “good” is doing a lot of work in that question — a ratio below the threshold with a waist above 88 cm is not the clean result it looks like, which is exactly the case the calculator above is built to catch.
Is waist-to-hip ratio better than BMI?
It measures something different. BMI is about overall size; the ratio is about where you carry weight. Neither is a health assessment on its own. If you want one simple number, current NICE guidance points at waist-to-height — keep your waist to less than half your height — which is easier to measure, needs no lookup table, and does not have a denominator that shrinks as you age.
Why did my ratio get worse when I have not gained weight?
Most likely one of two things, and both are common after 50. Either your hips have got smaller through loss of glute and thigh muscle, or fat has redistributed from your hips toward your waist at the same total weight. Check which number actually moved — a larger waist and a smaller hip measurement are different situations with different answers.
Should I measure at the narrowest point or at the navel?
Neither, strictly. WHO’s landmark is the midpoint between your lowest rib and the top of your hip bone. On many people that is close to the natural waist and close to the navel, but on plenty of people it is not, and the navel in particular shifts with age and weight. Find the bones.
Does a pear shape really mean lower risk?
On the evidence WHO reviewed, fat at the hips and thighs is associated with lower metabolic risk than fat around the organs. That is a population-level association, not a promise about any individual, and it does not mean a pear-shaped person with a large waist is in the clear. Which, again, is why the waist measurement is on the results page.
Are my measurements saved?
No. What you enter is sent to our server to be worked out and used only to produce the result on screen. Nothing is stored, logged against you or shared. This tool also has no shareable link, deliberately — a waist measurement does not belong in an address bar or a browser history.
