Particle Size Distribution of USGA Rootzone Mix

USDA System of Classification Sieve No. Sieve Opening (millimeters) Appro. Opening (inches) USGA Recommendations
Gravel
>2 mm
6
7
8
3.36
2.83
2.38
1/8" 3% max
S
A
N
D
Very coarse
1-2 mm
10
12
14
16
2.00
1.68
1.41
1.19
1/16" 7% max
Coarse
.5-1 mm
18
20
25
30
1.00
0.84
0.71
0.59
1/32" 60% min
Medium
.25-.5 mm
35
40
45
50
0.50
0.42
0.35
0.30
1/64"  
Fine
.1-.25 mm
60
70
80
100
0.25
0.21
0.177
0.149
1/128" 20% max
120
140
0.125
0.105
1/256"  
Very fine
.05-.1 mm
170
200
230
270
0.088
0.074
0.062
0.053
1/512" 5% maxa
Silt .002-.05 mm
Clay <.002 mm
325 0.044   5% maxa
3% maxa
aTotal particles in these ranges shall not exceed 10%