Waist-to-Hip Ratio (WHR) is the ratio of the waist to that of the hips. It is calculated by measuring the circumference of the waist, usually just above the belly button, and dividing by the circumference of the hip at its widest part. The ratio is applied both to women and men.
WHR is shown to be a good predictor of possible cardiovascular problems, such as heart attack, stroke, or other vascular disease, in both men and women. WHR is a better predictor than waist measurement alone and is a a better predictor than the body mass index (BMI).
For women, a ratio of .80 or less is considered safe (low risk in terms of vascular health). Some studies indicate 0.70 is ideal. For men it is 0.90 or less.