US and ASTM Std Sieve No. Actual Opening(in) (um)
10 0.0787 2000
12 0.0661 1680
14 0.0555 1410
16 0.0469 1190
18 0.0394 1000
20 0.0331 840
25 0.0280 710
30 0.0232 590
35 0.0197 500
40 0.0165 420
45 0.0138 350
50 0.0117 297
60 0.0098 250
70 0.0083 210
80 0.0070 177
100 0.0059 149
120 0.0049 125
140 0.0041 105
170 0.0035 88
200 0.0029 74
230 0.0024 62
270 0.0021 53
325 0.0017 44
400 0.00142 36
550 0.00099 25
625 0.00079 20
1250 0.000394 10
1750 0.000315 8
2500 0.00097 5
5000 0.000099 2.5
12000 0.0000394 1

Micrometer Comparisons

Substance (um)
Table Salt 100
Human Hair(average dia) 50-70
White Blood Cell 25
Talcum Powder 10
Cocoa 8-10
Red Blood Cell 8
Bacteria(cocci) 2
Note:Lower limit of visibility(naked eye)-40um
Relative Size of Particles
Magnification 500x
Linear Equivalents
1in =25.4mm =25,400um
1mm =0.0394in =1,000um
1um =1/25,400in =0.001mm
1um =3.94*10-5in =0.000039in
Formulas
velocity(ft per sec)=0.4085*9pm
d2ID in)
Conversion Rates
1 cu ft =7.48gal
1 gal =231 cu in
2 cu ft water =62.42lb
1 gal water =8.34lb
1 US gal =0.833lmp gal
1 lb/in2 =2.31ft of water=2.036 in Hg
0F =9/50C+32
Metric Conversion Formulas
mm =inches*25.4
m =feet*0.3048
cm3 =cu in *16.39
m3 =cu ft*0.028
kg =pounds*0.454
kPa =psi*6.895
lpm =gpm*3.785
0C =5/9(0F-32)