Dividing the circumference of a woman's waist by the circumference of her hips will give you her waist-hip ratio, a number that's very important when it comes to determining a woman's level of attractiveness. In Western cultures, a waist-hip ratio of 0.7 appears to be the one that men find most appealing on a woman, and research has found that it is linked to optimal levels of female reproductive hormones and a lower likelihood of a variety of diseases.