Skinfold Body Fat Calculator

The Jackson-Pollock (JP) method uses skinfold caliper measurements at specific body sites to estimate body density, then converts density to body fat percentage using the Siri equation. The 3-site JP method for men uses chest, abdominal, and thigh skinfolds. The 3-site JP method for women uses triceps, suprailiac, and thigh skinfolds. The equations were published by Jackson and Pollock in 1978 and 1980.

For men: Body Density = 1.10938 - (0.0008267 x sum) + (0.0000016 x sum squared) - (0.0002574 x age). For women: Body Density = 1.0994921 - (0.0009929 x sum) + (0.0000023 x sum squared) - (0.0001392 x age). Where sum is the sum of three skinfold measurements in millimeters. Body fat percentage is then calculated using the Siri equation: % Fat = (495 / Body Density) - 450.

With a trained tester and quality calipers, skinfold measurement has a standard error of approximately 3-4% body fat when compared to hydrostatic (underwater) weighing. Accuracy depends on technician skill, consistent site location, correct caliper pressure, and whether the subject has average fat distribution. The JP equations were validated on diverse adult populations.

According to the American College of Sports Medicine (ACSM): Essential fat is 2-5% (men) and 10-13% (women). Athletes: 6-13% (men) and 14-20% (women). Fitness: 14-17% (men) and 21-24% (women). Acceptable: 18-24% (men) and 25-31% (women). Obese: 25% or above (men) and 32% or above (women).

Use calibrated skinfold calipers. Grasp a double fold of skin and subcutaneous fat firmly between thumb and forefinger at the correct anatomical site. Apply the caliper 1 cm away from the fingers. Read the measurement after approximately 2 seconds when the needle stabilizes. Take two measurements at each site; if they differ by more than 1 mm, take a third. Use the average.