How to Measure Your Body Fat Percentage

Body composition testing (or body fat testing) measures the amount of body fat and fat-free mass, also referred to as lean tissue —muscle mass, body water, bone and organs— in the body.

We previously discussed Ideal body fat percentage ranges, Why measure body fat rather than BMI, and How to get rid of belly fat, but how do you actually measure body fat percentage?

If you want to lose fat rather than muscle, run faster or see some of the hard-earned muscle show through, you need to understand body composition.

Learning about your body composition is key to your optimal performance and appearance because it can help you strategize an exercise plan in terms of your need to lose fat, build muscle or both.

You might be weighing yourself once a month, once a week or even every day. You might also be calculating your body mass index (BMI) every now and then. But what if the extra weight you see on the scale was mostly muscle?

If you have a low body fat percentage, a heavy muscle mass and strong bones, you might be wrongly classified as overweight, because your BMI (and weight) would be high. A good way to know is to measure your body fat percentage, fat mass and fat-free mass.

Similarly, you could have a perfectly “healthy” BMI, you might still have a high body fat percentage, and a high amount of visceral fat —the fat that is stored within the abdominal cavity.

Knowing your what percentage of your weight is fat mass and fat-free mass will give you a more accurate view of your health. Thus, maintaining a healthy body composition is crucial to prevent disease. Moreover, if you know your fat mass and fat-free mass, you could easily plan your exercise and nutrition routine. So learning about body composition is also key for optimal performance and appearance.

Fortunately there are several techniques you could use to measure body composition. They all have advantages and disadvantages. Some of them are also a lot more accurate than others. Here are the top five techniques for measuring body composition (from the most accurate to least accurate):     

1- DEXA / DXA Scan

Advantages: The most precise and comprehensive method.

Disadvantages: Difficult to find 

How It Works:

Subject lies on a table fully clothed. A small dose of radiation passes through the body allowing X-rays to distinguish fat from muscle from bone.
*Special Note: Due to its ability to measure intramuscular fat the DEXA reading will typically be 3 to 8 percent higher body fat than all other methods of measurement.

Schedule a Fitnescity DEXA Body Composition Scan

2- BOD POD

Whole Body Plethysmography (Bod Pod)

Advantages: Very Accurate

Disadvantages: Difficult to find; Hard to pronounce

How It Works

Subject steps inside an egg shaped "pod" wearing as little clothing as possible. The pod measures the volume of air you displace, allowing the Bod Pod to measure your overall density. Since the density of an object (in this case your body) equals mass divided by volume, we know mass equals your body weight.
Volume is measured by the bod --pod. We know the density of fat , muscle and bone and water. The percentage of body fat can be calculated from overall body density.

Schedule a Fitnescity BOD POD Body Composition Test

3- Underwater/Hydrostatic Weighing

Advantages: Very accurate

Disadvantages: Difficult to find; You get wet during the test

How it Works:

Subject sits on a scale inside a giant tank of water. After exhaling all of the air from your lungs, you pull yourself underwater completely and sit very still for 10 seconds while the scale stabilizes. Underwater weighing also tries to measure a person's overall density.

Volume is calculated by measuring how much water your body displaces underwater. Volume equals your weight on land minus your weight under water. We know the density of fat , muscle and bone and water. The percentage of body fat can be calculated from overall body density.

4- Skinfold Calipers

Advantages: Reasonably accurate; Quick and easy to do

Disadvantages: Subject to high variability; Inaccurate if individual has localized body fat

How it works

Calipers are used to measure the thickness of two layers of skin plus the subcutaneous (that right under the skin) fat at four to six locations around the body. The most common locations are triceps, shoulder blade, abdomen, calf and love handle area. These measurements are totaled to arrive at a sum of skinfolds which is put on a table which equates skinfold total to percent body fat.

5- Bio-Impedence

Advantages: Quick and easy to do

Disadvantages: Readings are affected by hydration status and skin temperature; Inaccurate if individual has localized body fat 

How It Works

Subject either stands on a scale like device or holds an apparatus in outstretched hands and pushes a button. Button sends a very small current of electricity through that specific part of the body. Fat acts like the rubber insulation on a wire while muscle and bone and water all conduct electricity well. The larger the drop in current, the greater the body fat percentage.

*Special note: Since water and electrolytes both positively affect current flow, dehydration will cause body fat to be overestimated.

Be aware that since this machine only sends current through a specific part of the body, the accuracy of the readings are suspect. For example, most men do not store fat in their legs. If they are using a scale like device that send the electrical current through the legs, the overall body fat estimation will likely be low.

Body Fat Percentage Chart (learn more)

Bonus: Online Body Fat Percentage Calculator

The Online Body Fat Percentage Calculator can be used to estimate your total body fat percentage based on specific body measurements. The result might not be accurate as the one you would get from an actual body composition test, but it can give you an estimate. View the Online Body Fat Percentage Calculator.