Body fat measurement is an important factor in assessing nutritional status and general fitness. It is much more meaningful than weight alone, since the height-weight charts do not take into account body composition. The critical question is whether you are carrying too much body fat rather than too much weight, which can be due to muscularity. Using calipers to measure skin fold thickness, which is affected by underlying fat tissue, is one of the most practical methods of estimating your percentage of body fat.
Skin-fold Sites for Men
Step 1
Measure the chest skin fold. Locate the point that is one-half the distance between the top of the anterior axillary line and the nipple. The anterior axillary line starts at the fold of your armpit where your arm meets your torso on the front of your body. Mark and pinch a diagonal fold. Record your measurement.
Step 2
Measure the suprailiac skin fold. This is found in line with the natural angle of your hip bone. Mark the site just above your hip and in line with the anterior axillary line. Pinch a diagonal fold and record your measurement.
Step 3
Measure the abdominal skin fold. Measure a spot 2 cm to the right of the belly button or umbilicus. Mark and pinch a vertical skin fold and record your measurement.
Step 4
Measure the mid-axillary fold. This is found on the midline of your armpit along the side of your body at the level of the xiphoid process of your sternum. The xiphoid process is at the bottom of your sternum, underneath your pectorals where your ribs meet. Trace a horizontal line from the xiphoid to the right until you intersect with the mid-axillary line. Mark and pinch a vertical skin fold. Measure and record.
Step 5
Repeat measurements at all four sites.
Step 6
Use the sum of the skin folds in the following equation to calculate percentage of body fat for men:
%fat = 0.27784(sum of four skin folds) - 0.00053(sum of four skin folds squared) + 0.12437(age in years) - 3.28791
Skin-fold Sites for Women
Step 1
Only three skin fold sites are required for women. The first is the triceps skin fold. Locate a position on the back of the upper arm that is halfway between the bony point on top of your shoulder, or acromion process, and the bony point of your elbow, or olecranon process. Mark and pinch a vertical skin fold. Record your measurements.
Step 2
Measure the abdominal skin fold. Measure and mark the spot 2 cm to the right of the belly button or umbilicus. Pinch a vertical skin fold and record your measurement.
Step 3
Measure the suprailiac skin fold. This is found in line with the natural angle of your hip bone. Mark the site just above your hip and in line with the anterior axillary line. Pinch a diagonal fold and record your measurement.
Step 4
Repeat measurements at all three sites.
Step 5
Use the sum of the skin folds in the following equation to calculate percentage of body fat for women:
%fat = 0.41563(sum of three skin folds) - 0.00112(sum of three skin folds squared) + 0.03661(age in years) + 4.03653
Tips and Warnings
- When measuring skin folds, follow these guidelines from the American College of Sport's Medicine: Make all measurements on the right side of the body, place the caliper directly on the skin surface, 1 cm away from the thumb and the finger, perpendicular to the skin fold, and halfway between the crest and the base of the fold. Maintain your pinch while reading the caliper, wait 1 to 2 seconds, not longer, before reading the caliper. Take duplicate measures at each site and retest if not within 1 to 2 mm. Rotate through measurement sites.
- Poor technique, inexperience and an extremely obese or extremely lean subject can contribute to increased error.
Things You'll Need
- Body fat calipers
- Flexible measuring tape
- Washable pen or marker
- Calculator
References
- "Essentials of Strength Training and Conditioning"; Thomas R. Baechle and Roger W. Earle, Human Kinetics; 2000
- "ACSM's Guidelines for Exercise Testing and Prescription"; Lawrence Armstrong, Ph.D., et al.; 2006
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