Jackson-Pollock 4-Site Body Fat Calculator

About the Jackson-Pollock 4-Site Method

The Jackson-Pollock 4-site skinfold method was developed by Dr. Andrew Jackson and M.L. Pollock in 1985 as a practical middle ground between the simpler 3-site method and the more comprehensive 7-site method. It uses four measurement locations — tricep, suprailiac, abdomen, and thigh — which are the same for both males and females, simplifying the testing procedure.

Unlike the 3-site and 7-site methods (which calculate body density first), the 4-site equations output body fat percentage directly using sex- and age-specific regression equations.

4-Site Formulas

The sum of the four skinfold measurements (in mm) is plugged into these equations:

• Males: %BF = (0.29288 × sum) − (0.0005 × sum²) + (0.15845 × age) − 5.76377
• Females: %BF = (0.29669 × sum) − (0.00043 × sum²) + (0.02963 × age) + 1.4072

These equations were developed from large sample populations and have an estimated accuracy of ±3.5% compared to reference methods.

Comparing Skinfold Methods

Multiple skinfold methods exist, each with different sites and equations. Consider using several methods and comparing results for a more complete picture:

• Jackson-Pollock 3-Site — Different sites by sex, uses body density → Siri equation
• Jackson-Pollock 7-Site — Most comprehensive JP method with 7 measurement sites
• Durnin-Womersley 4-Site — Uses bicep, tricep, subscapular, suprailiac with age-specific coefficients
• Parrillo 9-Site — Uses 9 sites with a constant of 27 mm per 1% body fat
• US Navy Body Fat — Circumference-based method (no calipers needed)

How to Use This Calculator

1. Select your sex and unit system (metric or imperial)
2. Enter your age and body weight
3. Measure all four skinfold sites using calipers — take three readings per site and enter the average
4. Results update automatically: body fat %, fat mass, lean mass, and classification
5. Use the comparison table to see how different sum values affect the estimate at your age