Jackson-Pollock Body Fat Calculator (Skinfold)

Jackson-Pollock Skinfold Guide

What the Jackson-Pollock Method Is

The Jackson-Pollock equations are the research-standard way to estimate body fat from skinfold measurements taken with calipers. Developed by Andrew Jackson and Michael Pollock in the late 1970s, they remain among the most widely validated skinfold methods in exercise science. The method works in two stages. First, caliper measurements of skinfold thickness at several body sites are summed and used to estimate body density via a population-specific regression equation. Second, body density is converted to body fat percentage using the Siri equation: body fat percent = (495 / body density) − 450. Two common protocols exist: the 3-site (quick, three measurements) and the 7-site (more measurements, generally more accurate across a wider range of body types). The sites differ by sex because men and women store fat differently — the equations account for this. When performed carefully with quality calipers, Jackson-Pollock skinfold testing is accurate to roughly ±3-4% body fat, comparable to the Navy tape method and more accurate than BMI or basic bioelectrical impedance scales.

The 3-Site and 7-Site Protocols

The measurement sites depend on the protocol and sex. 3-site (men): chest, abdomen, thigh. 3-site (women): triceps, suprailiac, thigh. 7-site (both sexes): chest, abdomen, thigh, triceps, subscapular, suprailiac, and midaxillary. Site locations: chest — diagonal fold, midway between nipple and armpit (men) or one-third from armpit (women). Abdomen — vertical fold, 2cm right of the navel. Thigh — vertical fold, midway between hip and knee on the front of the thigh. Triceps — vertical fold, midway between shoulder and elbow on the back of the arm. Suprailiac — diagonal fold, just above the hip bone. Subscapular — diagonal fold, just below the shoulder blade. Midaxillary — vertical fold, on the midline of the side at nipple level. The 7-site protocol samples upper body, trunk, and lower body, so it captures fat distribution more completely — which is why it tends to be more accurate, particularly for very lean or athletic individuals. The 3-site is faster and adequate for routine tracking.

Taking Accurate Measurements

Skinfold accuracy depends heavily on technique — consistency matters more than anything. Measure on the right side of the body (standard convention). Pinch the skinfold firmly between thumb and forefinger about 1cm above the site, lifting the fat away from the muscle. Apply the caliper jaws to the fold, perpendicular to it, and read after 1-2 seconds (calipers compress over time). Take each measurement 2-3 times and use the average; re-measure if readings differ by more than 1-2mm. Don't measure after exercise (skin is engorged with blood and fluid), and stay consistent on time of day and hydration. Common errors: grabbing muscle as well as fat (grip too deep), inconsistent site location, reading the caliper too late, and using cheap plastic calipers with poor spring tension. Quality calipers (Harpenden, Lange, or good Slim Guide models) give far more reliable results. Skinfold testing has a learning curve — your first measurements will be your least reliable. For tracking change, the same person measuring the same sites the same way each time matters more than absolute accuracy.

Interpreting and Using Results

Once body fat percentage is calculated, interpret it against healthy ranges. Men: essential 2-5%, athletes 6-13%, fitness 14-17%, acceptable 18-24%, obese 25%+. Women: essential 10-13%, athletes 14-20%, fitness 21-24%, acceptable 25-31%, obese 32%+ (women carry more essential fat for hormonal health). The Jackson-Pollock result also gives body density and fat-free mass, which is useful for tracking whether weight changes are fat or muscle. Limitations to keep in mind: the equations were derived from specific populations and are least accurate at the extremes (very lean or very obese), where skinfold compressibility and fat distribution differ. They assume a standard relationship between subcutaneous and total body fat, which varies between individuals. For most people tracking fitness, that's fine. Compared with other methods: DEXA is the gold standard (±1-2%) but expensive; hydrostatic weighing is very accurate but impractical; the Navy tape method is convenient (±3-4%); bioelectrical impedance scales are convenient but variable (±5%, hydration-sensitive). Jackson-Pollock skinfolds, done well, sit in the accurate-and-affordable sweet spot — the main cost being the learning curve and a decent set of calipers. For medical concerns, consult a healthcare professional rather than self-directing from any body-fat figure.