The cholesterol/HDL ratio is a metric that helps determine a person's risk of developing heart disease, explains Mayo Clinic. A person with a high cholesterol/HDL ratio has a higher risk of developing heart disease than a person with a lower cholesterol/HDL ratio.
The cholesterol/HDL ratio is calculated by dividing a person's HDL measurement into his total cholesterol measurement, states Mayo Clinic. HDL, or high-density-lipoprotein, is known as good cholesterol. Using this calculation, a person with a total cholesterol of 200 milligrams per deciliter and an HDL of 50 milligrams per deciliter has a cholesterol/HDL ratio of 4-to-1. A cholesterol/HDL ratio of 3.5-to-1 is considered optimal, but most adults should aim for ratios of 5-to-1 or lower.