How does the Jackson-Pollock 3-site method work?

The Jackson-Pollock 3-site skinfold method is one of the most widely used and validated body fat estimation techniques in exercise science. Developed by Andrew Jackson and Michael Pollock in 1978, it uses skinfold measurements from three specific body sites to calculate body density, which is then converted to body fat percentage using the Siri equation.

The method uses different measurement sites for men and women. Men are measured at the chest, abdomen, and thigh. Women are measured at the triceps, suprailiac (above the hip bone), and thigh. Age is also factored into the formula because body composition changes as we age.

Measurement sites

For men

Chest: Diagonal fold halfway between the armpit crease and the nipple
Abdomen: Vertical fold approximately 2 cm to the right of the navel
Thigh: Vertical fold on the front of the thigh, midway between the hip and knee

For women

Triceps: Vertical fold on the back of the upper arm, midway between shoulder and elbow
Suprailiac: Diagonal fold just above the hip bone (iliac crest)
Thigh: Vertical fold on the front of the thigh, midway between the hip and knee

The formulas

This method uses a two-step process. First, body density is calculated from the skinfold sum and age:

Men (body density):
1.10938 - (0.0008267 x sum) + (0.0000016 x sum²) - (0.0002574 x age)

Women (body density):
1.0994921 - (0.0009929 x sum) + (0.0000023 x sum²) - (0.0001392 x age)

Siri equation (body fat):
% Body Fat = (495 / body density) - 450

All skinfold measurements are in millimeters. For the most accurate results, take each measurement twice and use the average. Use calipers with consistent pressure and measure on the right side of the body.

Try other methods

Don't have calipers? Try the U.S. Navy method or Covert Bailey method, both of which require only a tape measure. You can also enter a known value from a DEXA scan or scale using the manual entry option.