Rectangular Duct Sizes Chart

Rectangular Duct Sizes Chart

Duct Size(cfm) 4″
60 6×4
90 8×4
120 10×4
150 12×4
180 14×4
210 16×4
240 18×4
270 20×4
300 22×4
330 24×4
40 21/2×10
70 21/2×14
150 21/2×30
Duct Size(cfm) 6″
60 4×6
110 6×6
160 8×6
215 10×6
270 12×6
320 14×6
375 16×6
430 18×6
490 20×6
540 22×6
600 24×6
650 26×6
710 28×6
775 30×6
100 31/2×14
220 31/2×30
Duct Size(cfm) 8″
90 4×8
160 6×8
230 8×8
310 10×8
400 12×8
490 14×8
580 16×8
670 18×8
750 20×8
840 22×8
930 24×8
1020 26×8
1100 28×8
1200 30×8
1300 32×8
1400 34×8
1500 36×8
Duct Size(cfm) 10″
120 4×10
215 6×10
310 8×10
430 10×10
550 12×10
670 14×10
800 16×10
930 18×10
1060 20×10
1200 22×10
1320 24×10
1430 26×10
1550 28×10
1670 30×10
1800 32×10
1930 34×10
2060 36×10
2200 38×10
2350 40×10
Duct Size(cfm) 12″
150 4×12
270 6×12
400 8×12
550 10×12
680 12×12
800 14×12
950 16×12
1100 18×12
1250 20×12
1400 22×12
1600 24×12
1750 26×12
1950 28×12
2150 30×12
2300 32×12
2450 34×12
2600 36×12
2750 38×12
2900 40×12
3050 42×12

Rectangular Sheet Metal Duct = .07″ on most metal duct calculations

Round Duct Sizes Chart

Flexible Duct
Duct Size Design Airflow
5″ 50
6″ 75
7″ 110
8″ 160
9″ 225
10″ 300
12″ 480
14″ 700
16″ 1000
18″ 1300
20″ 1700

Flex Duct = .05″ on most metal duct calculations

Round Metal Pipe
Duct Size Design Airflow
5″ 50
6″ 85
7″ 125
8″ 180
9″ 240
10″ 325
12″ 525
14″ 750
16″ 1200
18″ 1500
20″ 2000

Round Metal Pipe = .06″ on most metal duct calculations

Leave a Reply