One tape measure and one division. It picks up the fat that sits around your organs - the kind that matters - and unlike BMI it does not call a muscular person overweight.
Nothing is sent anywhere - this runs inside your browser.
Enter your waist and height to see where you sit.
Keep your waist under half your height. That is the whole thing, and it is easy enough to remember without a calculator. A person 170 cm tall wants a waist under 85 cm. It works the same for men and women and across most of adult life, which is more than BMI manages.
BMI only knows your weight and your height. It cannot tell muscle from fat, so a lean, strong person often reads as overweight, and somebody light with a soft middle can read as perfectly fine. Waist to height measures where the fat actually is, and the fat around the organs is the kind linked to heart disease and type 2 diabetes.
Neither is a diagnosis. Both are a signal worth acting on, and this one is the more useful of the two - which is why it is here alongside the BMI calculator rather than instead of it.
Around your bare stomach at the level of your belly button, standing up, after breathing out normally. Do not suck in and do not pull the tape tight - it should sit against the skin without pressing. Measure at the same time of day each time, ideally in the morning, because a full stomach can add a couple of centimetres.
Risk from belly fat starts at a lower waist measurement for South Asian populations than for European ones, which is why Indian guidance uses tighter waist thresholds. The half-your-height rule already accounts for this better than a fixed number does, but it is worth knowing that being just under the line matters more here than it might elsewhere.
The waist comes down the same way everything else does - a calorie deficit, enough protein, and resistance training so what you lose is fat rather than muscle. Crunches will not do it, and the belly fat guide explains why. Measure your waist once a fortnight rather than daily; it moves slowly and honestly, which makes it a better progress marker than the scale.
A ratio is a screening signal, not a diagnosis. Everything on this page is worked out from a formula or from published averages. It has never met you, and it cannot see your blood pressure, your medication or an old injury.
Talk to a doctor before you start if you are pregnant or breastfeeding, have a heart condition, diabetes or high blood pressure, take regular medication, have or have had an eating disorder, are recovering from injury or surgery, or are under 18. Stop and get advice if any exercise causes pain, dizziness or chest discomfort.
More about where these numbers come from is on the about page.
