Ducts are the conduits or passages used in heating, ventilation, and air conditioning (HVAC) for delivering and removing air. Duct work is otherwise called as duct system. The length of the rectangular duct size would range from 0.7mm to 0.9mm galvanised mild steel depending on size. Provided here is the rectangular duct sizes chart for your personal reference and this chart / table shows the duct size (cfm) and their equivalent diameter in inches.
| 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 |
| 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 |
| 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 duct sizes chart helps you to find the size of duct with its corresponding inches. Here, equivalent diameter of rectangular ducts are given from 60 to 3050. For 375 duct size, the equivalent diameter inches will be about 16x6.
