Duct Sizing Calculator
Friction Loss per 100'
.04
.05
.06
.07
.08
.09
.10
.11
.12
.13
.14
Airflow (CFM)
50
75
100
125
150
175
200
250
300
350
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
3100
3200
3300
3400
3500
3600
3700
3800
3900
4000
4250
4500
4750
5000
5250
5500
5750
6000
6250
6500
6750
7000
7250
7500
7750
8000
8500
9000
9500
10000
Velocity (FPM)
Round Metal Size
Round Flex Size
Square Height (ID)
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
21
32
22
24
Sq. Width Metal (ID)
Sq. Width Duct Liner (ID)
Sq. Width Ductboard (ID)