Clinical Medicine & Physiology
Durnin-Womersley 4-Site Skinfold Calculator: LOG10 Skinfold Sum Body Density & %BF
Calculate Whole-Body Density D_b = c - m * LOG10(Biceps + Triceps + Subscapular + Suprailiac) and Siri Percent Body Fat across adult age-sex bands using J. V. G. A. Durnin and J. Womersley’s (1974, Br. J. Nutr.) general-population reference equations.
Linearize subcutaneous fat compression via base-10 logarithm LOG10(S_4)!
Published by Glasgow physiologists J. V. G. A. Durnin and J. Womersley (1974, British Journal of Nutrition) from underwater hydrostatic weighing of 481 men and women aged 16 to 72 years, the Durnin-Womersley 4-Site Protocol measures upper-body and trunk folds accessible without lower-body disrobing: Biceps + Triceps + Subscapular + Suprailiac = S_4 (mm)!
Taking the base-10 logarithm LOG10(S_4) linearizes the curvilinear relationship between subcutaneous caliper thickness and hydrostatic Whole-Body Density: D_b (g/cm^3) = c - m * LOG10(S_4)! Across the full 17–72 yr combined adult regression, Durnin & Womersley report (c = 1.1765, m = 0.0744) for Men and (c = 1.1567, m = 0.0717) for Women (with decade-specific constants such as Men 20–29: c = 1.1631, m = 0.0632; Men 30–39: c = 1.1422, m = 0.0544; Women 20–29: c = 1.1599, m = 0.0717; Women 30–39: c = 1.1423, m = 0.0632), followed by Siri’s equation %BF = (495 / D_b) - 450!
| Durnin-Womersley Cohort (20–29 vs 30–39 yr) | Intercept c & Slope m | At 4-Site Sum S_4 = 45 mm (LOG10 = 1.6532) | Siri Body Fat (%) |
|---|---|---|---|
| Adult Male 20–29 yr | c = 1.1631, m = 0.0632 | D_b = 1.05862 g/cm^3 | 17.59% BF |
| Adult Male 30–39 yr | c = 1.1422, m = 0.0544 | D_b = 1.05227 g/cm^3 | 20.41% BF |
| Adult Female 20–29 yr | c = 1.1599, m = 0.0717 | D_b = 1.04136 g/cm^3 | 25.34% BF |
| Adult Female 30–39 yr | c = 1.1423, m = 0.0632 | D_b = 1.03782 g/cm^3 | 26.96% BF |
Durnin-Womersley Predicted Body Density D_b = c - m * LOG10(SUM(4 Sites))
Evaluates c - m * LOG10(SUM(B2:B5)) from the 4 skinfolds in B2:B5 (mm) and age/sex-band intercept c (B6) & slope m (B7).
=IF(OR(MIN(B2:B5) <= 1, SUM(B2:B5) > 250, B6 < 1.1, B6 > 1.2, B7 <= 0, B7 > 0.12), "Invalid 4-Site Skinfolds (mm) or Durnin-Womersley Constants (c, m)", ROUND(B6 - B7 * LOG10(SUM(B2:B5)), 5))Durnin-Womersley + Siri Percent Body Fat (%BF = 495 / D_b - 450)
Converts Durnin-Womersley predicted body density directly into Siri two-compartment %BF.
=IF(OR(MIN(B2:B5) <= 1, SUM(B2:B5) > 250, B6 < 1.1, B6 > 1.2, B7 <= 0, B7 > 0.12), "Invalid 4-Site Skinfolds (mm) or Durnin-Womersley Constants (c, m)", ROUND((495 / (B6 - B7 * LOG10(SUM(B2:B5)))) - 450, 2))Try the example
Use the original values or change them to test your understanding.