### Description

Durnin and Womersley developed equations to estimate body density and percent body fat in adult men and women based on skinfold measurements.

Skinfold measurements:

(1) Measurements were usually taken on the right side with the patient in a relaxed condition.

(2) Sites measured: biceps, triceps, subscapular region, supra-iliac region

(3) The skinfold thickness is taken with a caliper tension of 9.8 * 10^4 newtons per square meter.

(4) Measurements <= 5 mm were taken to the nearest 0.5 mm; measurements > 5 mm were taken to the nearest mm.

(5) The authors found that subtracting 1.8 mm from each skinfold to take into account two layers of skin thickness during skinfold measurements did not improve results (page 80-81).

sum of 4 skinfolds =

= (thickness of biceps skinfold in mm) + (thickness of triceps skinfold in mm) + (thickness of subscapular skinfold in mm) + (thickness of supra-iliac skinfold in mm)

body density  in 1000 kg per cubic meter =

= c – (m * (LOG10 (total skinfolds in mm)))

where:

• 1 g per cc = 1000 kg per cubic meter

• Equations for the various combinations of skinfold thicknesses are given in Table 5, page 87.

• The standard errors for the equations are given in Table 4, page 82.

Male

Age in Years

c

m

17-19

1.1620

0.0630

20-29

1.1631

0.0632

30-39

1.1422

0.0544

40-49

1.1620

0.0700

50-72

1.1715

0.0779

from Table 5, page 86

Female

Age in Years

c

m

16-19

1.1549

0.0678

20-29

1.1599

0.0717

30-39

1.1423

0.0632

40-49

1.1333

0.0612

50-68

1.1339

0.0645

from Table 5, page 87

Siri Equation

percent body fat (from 0 to 100) =

= (((4.95 / (body density in grams per cubic cm)) - 4.5) * 100

Percent Body Fat

Male with Age in Years

Total Sum Skinfolds mm

17-29

30 – 39

40 – 49

50 - 72

15

4.8

20

8.1

12.2

12.2

12.6

25

10.5

14.2

15.0

15.6

30

12.9

16.2

17.7

18.6

35

14.7

17.7

19.6

20.8

40

16.4

19.2

21.4

22.9

45

17.7

20.4

23.0

24.7

50

19.0

21.5

24.6

26.5

55

20.1

22.5

25.9

27.9

60

21.2

23.5

27.1

29.2

65

22.2

24.3

28.2

30.4

70

23.1

25.1

29.3

31.6

75

24.0

25.9

30.3

32.7

80

24.8

26.6

31.2

33.8

85

25.5

27.2

32.1

34.8

90

26.2

27.8

33.0

35.8

95

26.9

28.4

33.7

36.6

100

27.6

29.0

34.4

37.4

105

28.2

29.6

35.1

38.2

110

28.8

30.1

35.8

39.0

115

29.4

30.6

36.4

39.7

120

30.0

31.1

37.0

40.4

125

30.5

31.5

37.6

41.1

130

31.0

31.9

38.2

41.8

135

31.5

32.3

38.7

42.4

140

32.0

32.7

39.2

43.0

145

32.5

33.1

39.7

43.6

150

32.9

33.5

40.2

44.1

155

33.3

33.9

40.7

44.6

160

33.7

34.3

41.2

45.1

165

34.1

34.6

41.6

45.6

170

34.5

34.8

42.0

46.1

175

34.9

180

35.3

185

35.6

190

35.9

195

200

205

210

from Table 9, page 95

Female with Age in Years

Skinfold mm

16-29

30 – 39

40 – 49

50 - 68

15

10.5

20

14.1

17.0

19.8

21.4

25

16.8

19.4

22.2

24.0

30

19.5

21.8

24.5

26.6

35

21.5

23.7

26.4

28.5

40

23.4

25.5

28.2

30.3

45

25.0

26.9

29.6

31.9

50

26.5

28.2

31.0

33.4

55

27.8

29.4

32.1

34.6

60

29.1

30.6

33.2

35.7

65

30.2

31.6

34.1

36.7

70

31.2

32.5

35.0

37.7

75

32.2

33.4

35.9

38.7

80

33.1

34.3

36.7

39.6

85

34.0

35.1

37.5

40.4

90

34.8

35.8

38.3

41.2

95

35.6

36.5

39.0

41.9

100

36.4

37.2

39.7

42.6

105

37.1

37.9

40.4

43.3

110

37.8

38.6

41.0

43.9

115

38.4

39.1

41.5

44.5

120

39.0

39.6

42.0

45.1

125

39.6

40.1

42.5

45.7

130

40.2

40.6

43.0

46.2

135

40.8

41.1

43.5

46.7

140

41.3

41.6

44.0

47.2

145

41.8

42.1

44.5

47.7

150

42.3

42.6

45.0

48.2

155

42.8

43.1

45.4

48.7

160

43.3

43.6

45.8

49.2

165

43.7

44.0

46.2

49.6

170

44.1

44.4

46.6

50.0

175

44.8

47.0

50.4

180

45.2

47.4

50.8

185

45.6

47.8

51.2

190

45.9

48.2

51.6

195

46.2

48.5

52.0

200

46.5

48.8

52.4

205

49.1

52.7

210

49.4

53.0

from Table 9, page 95

Approximating Equations from JMP

Males with Sum of Skinfolds <= 90 mm

percent fat for males 17-29 years old with skinfold 15-90 mm =

= (0.000041 * ((total skinfold)^3)) – (0.00932 * ((total skinfold)^2)) + (0.866067 * (total skinfold)) – 6.00107

percent fat for males 30-39 years old with skinfold 20-90 mm =

= (0.0000241 * ((total skinfold)^3)) – (0.006048 * ((total skinfold)^2)) + (0.6400706 * (total skinfold)) + 1.6609664

percent fat for males 40-49 years old with skinfold 20-90 mm =

= (0.0000365 * ((total skinfold)^3)) – (0.008677 * ((total skinfold)^2)) + (0.8749747 * (total skinfold)) – 2.002712

percent fat for males 50-72 years old with skinfold 20-90 mm =

= (0.0000429 * ((total skinfold)^3)) – (0.010065 * ((total skinfold)^2)) + (0.99782 * (total skinfold)) – 3.637384

Males with Sum of Skinfolds >= 90 mm

percent fat for males 17-29 years old with skinfold 90-190 mm =

= (0.0000015 * ((total skinfold)^3)) – (0.001 * ((total skinfold)^2)) + (0.285045 * (total skinfold)) + 7.5579898

percent fat for males 30-39 years old with skinfold 90-170 mm =

= (0.0000026 * ((total skinfold)^3)) – (0.0014* ((total skinfold)^2)) + (0.3141237 * (total skinfold)) + 8.9496

percent fat for males 40-49 years old with skinfold 90-170 mm =

= (0.0000014 * ((total skinfold)^3)) – (0.000961 * ((total skinfold)^2)) + (0.2892191 * (total skinfold)) + 13.707379

percent fat for males 50-72 years old with skinfold 90-170 mm =

= (0.0000002 * ((total skinfold)^3)) – (0.000594* ((total skinfold)^2)) + (0.274175 * (total skinfold)) + 15.78274

Females with Sum of Skinfolds <= 90 mm

percent fat for females 16-29 years old with skinfold 15-90 mm =

= (0.0000426 * ((total skinfold)^3)) – (0.009878 * ((total skinfold)^2)) + (0.94845 * (total skinfold)) – 1.432143

percent fat for females 30-39 years old with skinfold 20-90 mm =

= (0.0000323 * ((total skinfold)^3)) – (0.00782 * ((total skinfold)^2)) + (0.797252 * (total skinfold)) + 3.9435567

percent fat for females 40-49 years old with skinfold 20-90 mm =

= (0.0000351 * ((total skinfold)^3)) – (0.008319 * ((total skinfold)^2)) + (0.8182132 * (total skinfold)) + 6.4602618

percent fat for females 50-68 years old with skinfold 20-90 mm =

= (0.0000368 * ((total skinfold)^3)) – (0.008741 * ((total skinfold)^2)) + (0.8658072 * (total skinfold)) + 7.3191546

Females with Sum of Skinfolds >= 90 mm

percent fat for females 16-29 years old with skinfold 90-170 mm =

= (0.0000021 * ((total skinfold)^3)) – (0.001291 * ((total skinfold)^2)) + (0.3404369 * (total skinfold)) +13.092466

percent fat for females 30-39 years old with skinfold 90-200 mm =

= (0.0000005 * ((total skinfold)^3)) – (0.000519 * ((total skinfold)^2)) + (0.2163384 * (total skinfold)) + 20.274699

percent fat for females 40-49 years old with skinfold 90-200 mm =

= (0.0000009 * ((total skinfold)^3)) – (0.000711 * ((total skinfold)^2)) + (0.2388038 * (total skinfold)) + 21.965364

percent fat for females 50-68 years old with skinfold 90-210 mm =

= (0.0000011 * ((total skinfold)^3)) – (0.000801 * ((total skinfold)^2)) + (0.2600804 * (total skinfold)) + 23.492094