Skinfold Caliper Test

Measurement Technique

When measuring body fat using the skinfold method, repeatability is the key. To reduce measurement error, you need to perform the measurements the same way every time. So here are a few tips for improving your measurement technique:

Take all measurements on the same side of the body.

Place the calipers 1/2 inch below where you pinch with the thumb and finger. You’ll measure perpendicular to the skinfold. And remember, you don’t have to pinch hard. Your goal is to pull the full skinfold away from the body, not to squeeze the skin as hard as you can.

The pinch should be maintained while reading the caliper.

Wait 1-2 seconds after the pinch to take and read the measurement.

Measure each of the 7 sites once before returning for the second measurement. The same goes for the third measurement. The skin needs a chance to return to normal before it’s pinched again.

Again, take a minimum of 3 measurements at each site. Record the measurements and their average in Appendix A (Male Skinfold Measurement Worksheet) or Appendix B (Female Skinfold Measurement Worksheet).

Now, let’s talk about the 7 sites, where they’re located and how to measure them

Site 1: The Abdominal Site

This site is located 1 inch directly to the left of, and in line with, the umbilicus (belly button). You’ll want to pinch and measure a vertical fold of skin as demonstrated in the photographs below.

Site 2: The Triceps Site

This site is located at the back midline of the upper arm and halfway between the elbow and the bony point on the top of your shoulder. Measure this distance and mark the halfway point. Next, pinch a vertical fold of skin as demonstrated in the photographs below.

If you have a hard time with this particular site, flex your triceps (by extending your arm). This separates the muscle from the fat. Then, as the arm relaxes, it’s easier to grab the skinfold and take the measurement.

Site 3: The Chest Site

In men, this site is located on the diagonal line between the armpit and the nipple. Simply find the halfway point between the armpit and the nipple, and measure a
diagonal fold there.
In women, this site is located on the diagonal line between the armpit and the nipple,
just as with men. However, you’re going to measure 1/3 of the way between the two
locations, closer to the armpit.

Site 4: The Midaxillary Site

The midaxillary line is a vertical line between the armpit and the hip. Find this line and then find your skinfold site, which is on the same horizontal plane as your xyphoid process (the bony spot where your ribs meet at the center of your chest, also marked on the photos below). Select a vertical skinfold at this site.

It’s helpful to place your arm on top of your head while taking this measurement.

Site 5: The Subscapular Site

This site is just below your scapula (shoulder blade). To find the skinfold, trace a line parallel to and an inch below the lower angle of your shoulder blade. Take a skinfold measurement perpendicular to this line, as seen in the photos below.

Site 6: The Suprailiac Site

The suprailiac region is the area just above the natural frontal angle of the iliac crest (hip). To measure this spot, trace the front angle of the hip and select a diagonal fold of skin 0.5 to 1 inch above the hip bone.

Be consistent here from week to week as small deviations can produce fairly large changes in the readings.

Site 7: The Thigh Site

To select the thigh site, select a vertical fold on the front midline of the thigh, halfway between the kneecap and inguinal crease (the line where leg inserts into trunk). Measure this distance and mark the mid-point.

If you’re having a hard time with this one, it often helps to rest the foot of your leg on a box, chair, etc.

Now that you know the sites, where they’re located, and how to measure them, be sure to use Appendix A (Male Skinfold Worksheet) or Appendix B (Female Skinfold Worksheet) to record your 3 measurements.

The Skinfold Equations

The following equations will teach you how to determine your body fat % based on your measured skinfolds. I’ll warn you, they’re math-intensive. However, if you’ve got a calculator, you can get it done.

Male 7-Site Equation

Where SUM 7 = the sum of all 7 skinfold readings above, use the following equation to determine your body density:

Body Density = 1.112 – (0.00043499 * SUM7) + (0.00000055 * SUM72 ) – (0.00028826 * AGE)

Once you’ve calculated body density (Db), plug this into the equation to determine your body fat percentage:

%BF = [(4.57/ Db) – 4.142] * 100

Once you have your body fat percentage, calculate your lean mass as follows:

Fat mass (lbs or kg) = [Total body weight (lbs or kg) x body fat %] / 100

And once you have your fat mass, you can calculate your lean mass as follows:

Lean mass (lbs or kg) = Total body weight (lbs or kg) – fat mass (lbs or kg)

Female 7-Site Equation