How to Calculate Your Muscle to Fat Ratio

Body composition refers to the portion of your body that is fat versus muscle, bone and other fat-free tissue. Knowing your body fat percentage can be more useful in determining your health and fitness level than only knowing your total body weight or body mass index (BMI). That is because as body fat percentage increases, the risk of adverse health consequences increases. There are several methods to determine your body's ratio of fat versus fat-free mass. They range in cost, accuracy and the level of skill needed to perform the assessments.

A man is pinching the fat on his belly. (Image: Rasulovs/iStock/Getty Images)

Step 1

Submit to a skinfold measurement with calipers of three or seven sites on your body. This method for determining body fat percentage is the most widely used. It is also inexpensive and accurate to within 3 percent of body fat, although the accuracy may be adversely affected for those who are very overweight or very thin. It can be performed by anyone trained to use calipers that measure subcutaneous fat. University exercise physiology labs, YMCAs and other gyms are likely places to get skinfold measurements, which may be offered free or for a fee.

Step 2

Visit a research center or university exercise lab to submit to underwater weighing, also called hydrostatic weighing. This method predicts body fat percentage by submerging you underwater and measuring the buoyancy of your body. Since muscle and bone are dense they do not float, yet fat does.

You will be required to blow as much air from your lungs as possible before you're submerged. Underwater weighing is accurate to 1.5 percent and may range in cost from $10 to $75, according to the Georgia State University department of kinesiology. While hydrostatic weighing is the gold standard in body composition measurement, it may not be appropriate for people with anxiety surrounding water or submersion or those with lung health problems or problems holding still.

Step 3

Submit to a body composition test using the Bod Pod. This method uses air displacement to measure fat versus fat-free mass. It is available at university exercise labs and research labs at a fee ranging from $40 to $65, according to Georgia State University. During the test, you will be required to wear a swimming cap and tight-fitting clothing such as a bathing suit. You will sit inside the pod and remain still for up to eight minutes while the machine measures the air displacement. This method is accurate to within 3 percent but may not be appropriate for someone with claustrophobia. Participants must be enclosed in the Bod Pod; however, the door does not lock and there is a window that allows sight into and out of the machine.

Step 4

Complete a dual energy x-ray absorptiometry (DEXA) scan at a research lab or university exercise lab. This scan uses x-ray technology to provide estimates of fat, bone and muscle mass in the entire body and in specific areas of the body. It is more accurate than underwater weighing, yet more expensive at up to $300 per scan. Participants must lie flat on a table for up to 12 minutes during the scan but exposure to radiation is at safe, low levels.

Warning

Near infrared interactance and bioelectrical impedance are two other ways to measure body fat percentage. However, due to their inaccurate levels, they are not preferred methods.