Skinfold Body Fat Calculator (Jackson-Pollock)
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
Body fat percentage from skinfolds is calculated in two steps: body density from three skinfolds (a different formula per sex), then its conversion to a percentage via the Siri equation. For a 25-year-old man with skinfolds of 10, 15, and 12 mm (chest, abdomen, thigh), the result is about 10.7%.
Explanation
The 3-site Jackson-Pollock method estimates body density from the thickness of three folds of skin and subcutaneous fat tissue, measured with skinfold calipers at precise points on the body — three different sites depending on sex: chest, abdomen, and thigh for men, triceps, suprailiac, and thigh for women, these differences reflecting the fat storage areas that are statistically most representative for each sex. Once body density is obtained, the Siri equation (495 ÷ density − 450, published in 1961) converts it into a usable body fat percentage. This method is DIFFERENT from our US Navy method body fat calculator, which is based on simple neck, waist, and hip measurements with a tape measure rather than skinfolds: both techniques remain estimates, but the skinfold method, correctly performed by someone trained in the measurement (the main source of error in this method is precisely inter-operator variability, not the formula itself), is generally considered more accurate than circumference-based methods. The result nonetheless remains an ESTIMATE, far from the precision of a DEXA scan (dual-energy X-ray absorptiometry) or hydrostatic weighing, the reference laboratory methods.
Example: a 25-year-old man, skinfolds of 10, 15, and 12 mm
Inputs
Sex: male. Age: 25. Chest: 10 mm. Abdomen: 15 mm. Thigh: 12 mm.
Calculation
Sum of skinfolds = 10 + 15 + 12 = 37 mm. Density = 1.10938 − 0.0008267×37 + 0.0000016×37² − 0.0002574×25 ≈ 1.07455. %fat = 495 ÷ 1.07455 − 450 ≈ 10.66%.
Result
This profile corresponds to about 10.7% body fat.
Frequently asked questions
Why do the measurement sites differ between men and women?
Because the typical distribution of subcutaneous fat tissue differs statistically between the sexes: Jackson and Pollock calibrated the formulas separately on populations of men and women, each time selecting the three sites most representative of, and most predictive for, total body density for that sex, rather than a single set of sites applied to both.
What's the main source of error in this method?
Inter-operator variability in taking the measurement (pressure applied by the caliper, exact site location, pinching technique) is generally cited as the main source of error, more so than the mathematical formula itself. The same operator measuring consistently over time gives a reliable trend, even if the absolute value differs slightly from one examiner to another.
Is this method more accurate than the body-circumference calculation (US Navy method)?
Validation studies generally cite a well-performed skinfold method as slightly more accurate than circumference-based methods like the US Navy method, since it directly measures subcutaneous fat thickness rather than inferring body composition from overall silhouette. Both remain field estimates, though, far from the precision of a lab DEXA scan or hydrostatic weighing.
What can this body fat percentage be used for?
It notably allows calculating lean body mass (total weight minus fat mass), itself used by indicators like our fat-free mass index calculator (FFMI), which compares this lean mass to height to assess muscular development independent of body fat, or by resting metabolic rate formulas based on lean mass rather than total weight.