Circular Duct Sizes

Dimensions of circular ventilation air ducts

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Circular galvanized steel duct

Circular Duct Dimensions - Metric Units

Common circular duct sizes used in air handling ventilation systems:

Nominal Diameter
(mm)		 Outside Diameter
(mm)		 Inside Diameter
(mm)
63 63 - 63.5 61.8 - 62.3
80 80 - 80.5 78.8 - 79.3
100 100 - 100.5 98.8 - 99.3
125 125 - 125.5 123.8 - 124.3
160 160 - 160.6 158.7 - 159.3
200 200 - 200.7 198.6 - 199.3
250 250 - 250.8 248.5 - 249.3
315 315 - 315.9 313.4 - 314.3
400 400 - 401.0 398.3 - 399.3
500 500 - 501.1 498.2 - 499.3
630 630 - 631.2 628.1 - 629.3
800 800 - 801.6 798.0 - 799.3
1000 1000 - 1002.0 997.9 - 999.3
1250 1250 - 1252.5 1247.8 - 1249.3

Circular Galvanized Steel Ducts - Areas and Weights - Imperial Units

Diameter
(inches)		 Surface Area
(ft2/ft)		 Gage
26 24 22
Weight (lbs/ft)
4 1.05 1.02 1.36 1.59
5 1.31 1.25 1.67 1.95
6 1.57 1.49 1.98 2.32
7 1.83 1.72 2.30 2.69
8 2.09 1.96 2.61 3.06
9 2.36 2.20 2.93 3.42
10 2.62 2.51 3.34 3.91
11 2.88 2.74 3.66 4.28
12 3.14 2.98 3.97 4.64
13 3.40 3.21 4.28 5.01
14 3.67 3.45 4.60 5.38
15 3.93 3.68 4.91 5.75
16 4.19 3.92 5.23 6.12
17 4.45 4.16 5.54 6.48
18 4.72 4.39 5.85 6.85
19 4.98 4.63 6.17 7.22
20 5.24 4.94 6.58 7.70
21 5.50 5.18 6.90 8.07
22 5.75 5.41 7.21 8.44
23 6.02 5.64 7.53 8.80
24 6.28 5.88 7.84 9.17
25 6.54 6.12 8.15 9.54
26 6.80 6.35 8.47 9.91
Gage
24 22 20
27 7.07 8.78 10.27 12.47
28 7.33 9.10 10.64 12.92
29 7.59 9.41 11.01 13.36
30 7.85 9.83 11.50 13.95
31 8.11 10.14 11.86 14.40
32 8.38 10.45 12.23 14.84
33 8.65 10.77 12.67 15.29
34 8.91 11.08 12.96 15.75
35 9.17 11.40 13.33 16.18
36 9.43 11.71 13.70 16.63
37 9.69 12.02 14.07 17.07
38 9.95 12.34 14.44 17.52
39 10.21 12.65 14.80 17.97
40 10.47 13.07 15.29 18.55
41 10.73 13.39 15.66 19.00
42 10.99 13.70 16.02 19.45
43 11.26 14.01 16.39 19.89
44 11.52 14.32 16.76 20.34

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  • Ventilation - Systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more

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