The formula
How to calculate waist to height ratio
Waist to height ratio is the simplest useful measure of central obesity, and the easiest to remember: your waist should be less than half your height. NICE adopted it in UK guidance in 2022 as a companion to BMI.
Because both measurements are in the same units, the ratio works with any tape and needs no adjustment for sex or age — the same 0.5 threshold applies to adults regardless.
What to enter:
- Waist circumference (cm)
- Height (cm)
Everything recalculates as you type, and the numbers in the address bar update with it, so a link to this page carries your figures with it.
Consistency in how the underlying measurements are taken matters more than precision to the last decimal — measuring at the same time of day, in the same state of rest or hydration, makes readings taken weeks apart genuinely comparable in a way that a single very precise reading on its own is not.
Why waist to height ratio matters
The formula behind waist to height ratio comes from published research rather than being invented for this page, and it is presented here exactly as it appears in the literature it is drawn from — the value of a calculator is applying it correctly and instantly, not reinventing it.
This tends to get checked before or after a change in routine — a new training block, a change in diet, a different stage of a pregnancy — as a way of putting a figure on something that would otherwise only be felt rather than measured.
None of the figures produced on this page are intended to replace a proper assessment, and nothing here should be read as a diagnosis or a treatment recommendation. What a calculator like this is good for is preparation — arriving at an appointment with an actual number already in hand, rather than a vague sense of a change, tends to make that conversation more useful for everyone involved.
In practice, this kind of figure is often calculated more than once with slightly different inputs to see how sensitive it is — trying a measurement taken this morning against one taken yesterday evening, for instance, to see how much normal daily variation actually moves the result. That habit is a good one: it builds a feel for how much a single reading can be trusted on its own before drawing any conclusion from it.
Worked example
Here is the calculation with the starting values:
- Waist circumference: 88 cm
- Height: 175 cm
That gives:
- Waist to height ratio: 0.503
- Waist at a 0.5 ratio: 87.5 cm
- Centimetres above that target: 0.5 cm
Those starting figures exist only to show the calculation working, not as a target or a reference value to compare yourself against — replace them with your own measurements in the calculator above and the same formula applies exactly as shown.
Reading the result
Below 0.5 is the healthy range. Between 0.5 and 0.6 indicates increased risk, and above 0.6 substantially increased risk. The target figure above is the waist measurement that would bring you to 0.5.
Where this goes wrong. Measure at the right place — midway between the lowest rib and the hip bone, not at the trouser line, which is usually several centimetres lower and gives a flattering reading. This is general information, not a medical assessment.
As with any general-purpose formula, the result here is an estimate derived from population averages, not a measurement specific to you — a reasonable starting point for a conversation with a qualified professional, not a replacement for one. Nothing on this page is medical advice.
Because BMI misses where fat is stored. Two people with the same BMI can carry very different amounts of visceral fat, and the waist measurement is what distinguishes them.
It is used for children over five, with the same threshold. It is not applied to younger children, where growth patterns make it unreliable.
The headline figure is waist to height ratio. With 88 cm waist circumference and 175 cm height, that comes to 0.503. Change any field and the figure moves with it.
It uses a published formula applied exactly as defined, so the arithmetic itself is precise — but the formula is a population-level estimate, and individual results can vary from it for reasons the formula has no way to account for. Treat the output as a reasonable estimate rather than a measured or diagnostic value.
For most people, yes — a single reading is a snapshot, while the same measurement repeated consistently over weeks or months shows a trend, which is generally more informative than any one figure taken in isolation.
Small differences between calculators usually come down to which published formula or reference dataset each one uses — several equations in this area exist in more than one accepted version. This page states the specific formula used in the section above, so it is possible to check directly whether another source is using the same one.