HVAC Duct Sizing Chart - 0.1 in.w.g./100ft

Round Diameter (in)	Round Velocity (FPM)	Round Area (sq ft)	CFM	Rect Area (sq ft)	Rect Velocity (FPM)	Rectangular Size (in)
4	401	0.087	35	0.167	210	6 × 4
5	477	0.136	65	0.194	334	7 × 4
6	535	0.196	105	0.222	473	8 × 4
7	599	0.267	160	0.347	461	10 × 5
8	659	0.349	230	0.458	502	11 × 6
9	713	0.442	315	0.500	630	12 × 6
10	761	0.545	415	0.681	610	14 × 7
11	811	0.660	535	0.833	642	15 × 8
12	859	0.785	675	0.889	759	16 × 8
13	906	0.922	835	1.125	742	18 × 9
14	949	1.069	1015	1.319	769	19 × 10
15	994	1.227	1220	1.389	878	20 × 10
16	1038	1.396	1450	1.681	863	22 × 11
17	1079	1.576	1700	1.917	887	23 × 12
18	1118	1.767	1975	2.000	988	24 × 12
19	1158	1.969	2280	2.257	1010	25 × 13
20	1199	2.182	2615	2.625	996	27 × 14
21	1235	2.405	2970	2.722	1091	28 × 14
22	1273	2.640	3360	3.021	1112	29 × 15
23	1310	2.885	3780	3.444	1097	31 × 16
24	1346	3.142	4230	3.556	1190	32 × 16

Round Diameter (in)

Round Velocity (FPM)

Round Area (sq ft)

CFM

Rect Area (sq ft)

Rect Velocity (FPM)

Rectangular Size (in)

401

0.087

0.167

210

6 × 4

477

0.136

0.194

334

7 × 4

535

0.196

105

0.222

473

8 × 4

599

0.267

160

0.347

461

10 × 5

659

0.349

230

0.458

502

11 × 6

713

0.442

315

0.500

630

12 × 6

761

0.545

415

0.681

610

14 × 7

811

0.660

535

0.833

642

15 × 8

859

0.785

675

0.889

759

16 × 8

906

0.922

835

1.125

742

18 × 9

949

1.069

1015

1.319

769

19 × 10

994

1.227

1220

1.389

878

20 × 10

1038

1.396

1450

1.681

863

22 × 11

1079

1.576

1700

1.917

887

23 × 12

1118

1.767

1975

2.000

988

24 × 12

1158

1.969

2280

2.257

1010

25 × 13

1199

2.182

2615

2.625

996

27 × 14

1235

2.405

2970

2.722

1091

28 × 14

1273

2.640

3360

3.021

1112

29 × 15

1310

2.885

3780

3.444

1097

31 × 16

1346

3.142

4230

3.556

1190

32 × 16

Note: 6 × 4 represents the minimum practical rectangular duct size for most HVAC applications.

Standard Friction Rate Applications (0.1 in.w.g./100ft)

This friction rate is the industry standard for most residential and commercial HVAC systems. Provides a good balance between duct size, energy efficiency, and cost-effectiveness for typical installations.

Design Notes for 0.1 in.w.g./100ft Systems

Industry Standard: Most commonly used friction rate in residential and commercial applications
Balanced Design: Good compromise between duct size, energy use, and material costs
Moderate Velocities: Acceptable noise levels for most occupied spaces
Cost Effective: Smaller ducts than low-friction systems reduce installation costs
Versatile Application: Suitable for offices, retail, restaurants, and residential buildings
Energy Consideration: Higher friction than 0.08 systems increases fan energy slightly

HVAC Professional Tools

HVAC Duct Sizing Chart - 0.1 in.w.g./100ft

Round and Rectangular Duct Equivalents

Standard Friction Rate Applications (0.1 in.w.g./100ft)

Design Notes for 0.1 in.w.g./100ft Systems

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