Measurement and Conversion Charts

Chart 1:
CFM requirements for diameter at specified velocity
Diameter 3500 FPM 4000 FPM 4500 FPM
3" 170 195 220
4" 300 350 390
5" 475 550 610
6" 700 785 880
7" 950 1100 1200
8" 1200 1400 1570
9" 1550 1800 1990
10" 1900 2200 2450
12" 2800 3175 3600
14" 3800 4300 4800
  Chart 2:
Static Pressure based on 100' of Pipe
Diameter 3500 FPM 4000 FPM 4500 FPM
3" 7.5 10.0 12.0
4" 5.5 7.0 8.5
5" 4.2 5.5 6.5
6" 3.5 4.5 5.5
7" 2.8 3.8 4.5
8" 2.4 3.2 3.8
9" 2.0 2.8 3.4
10" 1.8 2.4 3.0
12" 1.2 2.0 2.5
14" 1.3 1.6 2.0


Chart 3:
Elbow to Straight Pipe Conversion
Diameter 90° Elbow
1.5 Diameter Rad.
45° Elbow
1.5 Diameter Rad.
3" 5' 2.5'
4" 6' 3'
5" 9' 4.5'
6" 12' 6'
7" 12' 6.5'
8" 15' 7.5'
9" 17.5' 8.75'
10" 20' 10'
12" 25' 12.5'
14" 30' 15'


Static pressure of two 4" branches (350 CFM each) and one 5" branch (550 CFM) pulling vacuum simultaneously = Total 1,250CFM.