Grain Size Scale

U. S. Standard Sieve Mesh mm Phi (Φ) Units Wentworth Size Class
  4096 -12 boulder gravel
  1024 -10
  256 -8
  64 -6 cobble
     
  16 -4 pebble
5 4 -2
6 3.36 -1.75 granule
7 2.83 -1.5
8 2.38 -1.25
10 2 -1
12 1.68 -0.75 very coarse sand sand
14 1.41 -0.5
16 1.19 -0.25
18 1 0
20 0.84 0.25 coarse sand
25 0.71 0.5
30 0.59 0.75
35 0.5 1
40 0.42 1.25 medium sand
45 0.35 1.5
50 0.3 1.75
60 0.25 2
70 0.21 2.25 fine sand
80 0.177 2.5
100 0.149 2.75
120 0.125 3
140 0.105 3.25 very fine sand
170 0.088 3.5
200 0.074 3.75
230 0.0625 4
270 0.053 4.25 coarse silt silt mud
325 0.044 4.5
  0.037 4.75
  0.031 5
  0.0156 6 medium silt
  0.0078 7 fine silt
  0.0039 8 very fine silt
  0.002 9 clay clay
  0.00098 10
  0.00049 11
  0.00024 12
  0.00012 13
  0.00006 14

Modified from: Boggs, S., Jr., 1995, Principles of Sedimentology and Stratigraphy: Upper Saddle River, Prentice-Hall, Inc., 774 p. (after Wentworth, 1922)

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