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Engineering ToolBox > Circular Duct Sizes
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 |