The percentage of muscle mass in the human body depends upon gender, age and physical fitness. For men, the average muscle mass is between 38 percent and 54 percent, while for women the range is between 28 percent and 39 percent.
Knowing one's muscle mass percentage is helpful in maintaining a healthy weight. A person who has a higher muscle mass expends more energy in order to perform movements but may have an easier time achieving movement.
Most tests to determine percentages of body weight focus on body mass index, or the total fat percentage. For men, 16 percent body fat is considered to be normal, while 27 percent is considered normal for women.