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Clinical Medicine & Physiology

Jackson-Pollock 3-Site Skinfold Calculator: Body Density & Siri Body Fat % (Men & Women)

Calculate caliper skinfold sum S_3 (mm), quadratic Whole-Body Density D_b (g/cm^3), and Siri Percent Body Fat using Jackson & Pollock (1978, Men: Chest + Abdomen + Thigh) and Jackson, Pollock & Ward (1980, Women: Triceps + Suprailiac + Thigh).

Why Jackson & Pollock introduced quadratic skinfold sum S_3^2 to eliminate curvilinearity across lean and obese adults!

Earlier linear skinfold equations worked only inside narrow age/fatness sub-cohorts because subcutaneous fat compresses non-linearly at high caliper thicknesses! Andrew S. Jackson and Michael L. Pollock (1978, Br. J. Nutr. for Men aged 18–61; 1980, Jackson, Pollock & Ward, Med. Sci. Sports Exerc. for Women aged 18–55) introduced quadratic sum-of-3-skinfolds S_3 (in mm) plus age adjustment to predict hydrostatic Body Density D_b across the entire athletic-to-obese spectrum!

For Men (S_3 = Chest + Abdomen + Thigh, mm): D_b = 1.10938 - 0.0008267 * S_3 + 0.0000016 * (S_3^2) - 0.0002574 * Age! For Women (S_3 = Triceps + Suprailiac + Thigh, mm): D_b = 1.0994921 - 0.0009929 * S_3 + 0.0000023 * (S_3^2) - 0.0001392 * Age! Plugging D_b directly into Siri’s equation (495 / D_b) - 450 yields Percent Body Fat (%BF)!

Sex & 3-Site Caliper ProtocolExample Skinfolds (mm) & AgePredicted Body Density D_bSiri Body Fat (%)
Male (Chest 10, Abdomen 18, Thigh 14; Age 30)S_3 = 42 mm1.06975 g/cm^312.72% BF
Female (Triceps 16, Suprailiac 15, Thigh 23; Age 30)S_3 = 54 mm1.04841 g/cm^322.14% BF

Jackson-Pollock 3-Site Predicted Whole-Body Density D_b (g/cm^3)

Sums the three sex-appropriate caliper folds SUM(B4:B6) (mm) and evaluates Male ("M") or Female ("F") quadratic body density for Age B3 (18–75 yr).

=IF(OR(AND(B2 <> "M", B2 <> "F"), B3 < 18, B3 > 75, MIN(B4:B6) <= 1, SUM(B4:B6) > 220), "Invalid Sex (M/F), Adult Age (18–75), or Skinfolds (mm)", ROUND(IF(B2 = "M", 1.10938 - 0.0008267 * SUM(B4:B6) + 0.0000016 * (SUM(B4:B6) ^ 2) - 0.0002574 * B3, 1.0994921 - 0.0009929 * SUM(B4:B6) + 0.0000023 * (SUM(B4:B6) ^ 2) - 0.0001392 * B3), 5))

Jackson-Pollock + Siri Percent Body Fat (%BF = 495 / D_b - 450)

Converts unrounded Jackson-Pollock 3-site body density directly into Siri %BF.

=IF(OR(AND(B2 <> "M", B2 <> "F"), B3 < 18, B3 > 75, MIN(B4:B6) <= 1, SUM(B4:B6) > 220), "Invalid Sex (M/F), Adult Age (18–75), or Skinfolds (mm)", ROUND((495 / IF(B2 = "M", 1.10938 - 0.0008267 * SUM(B4:B6) + 0.0000016 * (SUM(B4:B6) ^ 2) - 0.0002574 * B3, 1.0994921 - 0.0009929 * SUM(B4:B6) + 0.0000023 * (SUM(B4:B6) ^ 2) - 0.0001392 * B3)) - 450, 2))

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