Waist to Height Ratio. The waist-to-height ratio is calculated by measuring waist size and dividing it by height, in inches. For example, a man with a 36-inch waist who is 6 feet 3 inches, or 75 inches total, would have a ratio of .48.octors are increasingly using BMI in combination with waist circumference to assess a person’s risk. Men with a waist size of more than 40 inches and women with a waist size of more than 35 inches are at increased risk for heart disease and diabetes.