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Durnin & Womersley 4-Site Skinfold Calculator: Body Fat Percentage

By PounceFit Team · Updated on

Trainer coaching a client through a dumbbell exercise
Photo: PTPioneer (CC BY 2.0), via Flickr

Technical content for health and fitness professionals. It reproduces formulas and protocols published in the scientific literature, with the sources at the end of the page. It is not a recommendation and does not replace the judgment of the professional who runs the assessment.

Free Durnin & Womersley 4-site skinfold calculator: body fat percentage by sex and age band, with the same math as PounceFit, the body assessment app.

The Durnin & Womersley 4-site skinfold calculator estimates body fat percentage from four skinfolds: biceps, triceps, subscapular and suprailiac. Body density comes from the logarithm of the skinfold sum, with separate coefficients for each sex and age band (Durnin and Womersley, 1974), and the Siri equation (1961) converts it to body fat. The math is the same as in PounceFit, body assessment software.

Who it is for

Adults across a wide age range. The original study measured 481 men and women aged 16 to 72 (Durnin and Womersley, 1974). PounceFit and this calculator accept clients aged 17 and older and show a warning below that age.

Formula

S = sum of the four skinfolds, in mm. log is the base-10 logarithm.

  • Density = c − m × log(S)
  • Body fat (%) = (4.95 ÷ density − 4.50) × 100

Coefficients c and m by age band (Durnin and Womersley, 1974):

Age Men c Men m Women c Women m
up to 19 1.1620 0.0630 1.1549 0.0678
20 to 29 1.1631 0.0632 1.1599 0.0717
30 to 39 1.1422 0.0544 1.1423 0.0632
40 to 49 1.1620 0.0700 1.1333 0.0612
50 or older 1.1715 0.0779 1.1339 0.0645

Worked example

Woman, 42 years old, 68 kg (150 lb). Skinfolds (mm): biceps 8, triceps 20, subscapular 16, suprailiac 18.

  1. S = 62 mm; log(62) = 1.7924.
  2. Age band 40 to 49, women: c = 1.1333 and m = 0.0612.
  3. Density = 1.1333 − 0.0612 × 1.7924 = 1.0236056.
  4. Body fat = (4.95 ÷ 1.0236056 − 4.50) × 100 = 33.6%.
  5. Fat mass = 22.8 kg; fat-free mass = 45.2 kg.

Limitations

  • Moving to a new age band changes the coefficients. On a client's 30th, 40th or 50th birthday, the result can shift with no change in the skinfolds.
  • The result is an estimate (Heyward and Wagner, 2004). The Siri conversion assumes fixed densities for fat mass and fat-free mass (Siri, 1961).
  • Use the standardized measurement sites (ACSM, 2021) and keep the same protocol at every reassessment.

Sources

  1. Durnin JVGA, Womersley J. Body fat assessed from total body density and its estimation from skinfold thickness: measurements on 481 men and women aged from 16 to 72 years. British Journal of Nutrition. 1974;32(1):77-97. doi:10.1079/BJN19740060
  2. Siri WE. Body composition from fluid spaces and density: analysis of methods. In: Brožek J, Henschel A, editors. Techniques for measuring body composition. Washington: National Academy of Sciences; 1961. p. 223-244.
  3. Heyward VH, Wagner DR. Applied body composition assessment. 2nd ed. Champaign: Human Kinetics; 2004.
  4. American College of Sports Medicine. ACSM's guidelines for exercise testing and prescription. 11th ed. Philadelphia: Wolters Kluwer; 2021.