Healthy muscle and body fat percentage varies from person to person and depends mainly on a person's level of physical activity. According to fitness expert Jillian Michaels, the healthy range of muscle mass for women is between 20 and 21 percent and for men it is 13 to 17 percent.
Michaels notes that it is best to refer to a person's body fat percentage to determine whether their muscle mass is in correct proportion to their height and weight. Shape Up America's Healthy Range of Body Fat chart shows the differences in healthy body fat percentage numbers for men and women of various ages. According to the chart, women should have a body fat percentage between 21 and 35 percent and men should have a body fat percentage between 8 and 24 percent.