Specifications
- Inlet Width: 2" to 48"
- Inlet Thickness: 2" to 48"
- Outlet Diameter: 2" to 48"
- Length: 4" to 36"
- Materials: Galvanized Steel, Aluminum, Stainless Steel
- Gauges: 26, 24, 22, 20
- Connections: Raw, Slip, Drive, TDC, Flanged
Standard Square to Round Transition Sizes & Pricing
| Inlet W | Inlet H | Outlet Dia | Length | Material | Gauge | Inlet | Outlet | Price | Order |
|---|---|---|---|---|---|---|---|---|---|
| 8"x8" | 6" | 8" | Galvanized | 26 ga | Slip / Slip | $36.82 | |||
| 10"x8" | 6" | 8" | Galvanized | 26 ga | Slip / Slip | $38.06 | |||
| 10"x8" | 8" | 8" | Galvanized | 26 ga | Slip / Slip | $40.02 | |||
| 10"x10" | 8" | 10" | Galvanized | 26 ga | Drive / Drive | $48.33 | |||
| 12"x8" | 6" | 8" | Galvanized | 26 ga | Drive / Drive | $41.31 | |||
| 12"x8" | 8" | 10" | Galvanized | 26 ga | Drive / Drive | $48.33 | |||
| 12"x10" | 8" | 10" | Galvanized | 26 ga | Drive / Drive | $49.88 | |||
| 12"x12" | 10" | 10" | Galvanized | 26 ga | Drive / Drive | $53.88 | |||
| 14"x8" | 8" | 10" | Galvanized | 26 ga | TDC / TDC | $53.88 | |||
| 14"x10" | 10" | 10" | Galvanized | 26 ga | TDC / TDC | $57.88 | |||
| 14"x12" | 10" | 12" | Galvanized | 24 ga | TDC / TDC | $79.71 | |||
| 16"x10" | 10" | 10" | Galvanized | 24 ga | TDC / TDC | $71.93 | |||
| 16"x12" | 12" | 12" | Galvanized | 24 ga | TDC / TDC | $85.47 | |||
| 18"x12" | 10" | 12" | Galvanized | 24 ga | TDC / TDC | $84.19 | |||
| 18"x14" | 12" | 12" | Galvanized | 22 ga | TDC / TDC | $113.19 | |||
| 20"x12" | 12" | 12" | Galvanized | 22 ga | Flanged / Flanged | $121.19 | |||
| 20"x14" | 14" | 14" | Galvanized | 22 ga | Flanged / Flanged | $141.45 | |||
| 24"x12" | 14" | 14" | Galvanized | 22 ga | Flanged / Flanged | $144.72 | |||
| 24"x18" | 16" | 14" | Galvanized | 22 ga | Flanged / Flanged | $159.65 | |||
| 24"x24" | 18" | 14" | Galvanized | 20 ga | Flanged / Flanged | $228.11 | |||
| 12"x10" | 8" | 10" | Aluminum | 26 ga | Drive / Drive | $68.37 |
Custom Square to Round Duct Transitions — Rectangular to Round Adapters
Square to round transitions are essential fittings that bridge rectangular trunk lines with round branch duct or equipment connections. Our transitions are fabricated as a single tapered shell that smoothly converts the cross-section from rectangular to circular, minimizing turbulence and pressure drop. Each piece is custom sized to your exact inlet and outlet dimensions.
Common Applications
The most frequent use is connecting rectangular trunk lines to round register boots or flexible duct takeoffs. Residential systems often need 10"×8" to 6" round or 12"×12" to 8" round transitions. Commercial applications include adapting rectangular plenums to round spiral duct runs and connecting air handling units with rectangular outlets to round distribution duct.
Sizing & Airflow Considerations
For optimal airflow, the transition length should be at least 1.5 times the larger dimension of the rectangular inlet. Abrupt transitions create excessive turbulence and noise. Our standard lengths range from 4" to 36", with custom lengths available. The outlet diameter should provide equivalent or greater cross-sectional area to the inlet to maintain airflow velocity.
Material & Construction
Each transition is CNC plasma-cut and hand-formed to produce the complex geometry required for a smooth rectangular-to-round conversion. Galvanized steel is the standard material. Aluminum is available for weight-sensitive installations. Stainless steel is specified for grease duct, clean room, and marine environments. All seams are Pittsburgh-locked for rigidity.
Frequently Asked Questions
When do I need a square-to-round transition?
Use a square-to-round adapter when connecting rectangular trunk duct to round branch runs, flex duct takeoffs, or diffuser boots.
Can the round end be offset from center?
Our standard adapters center the round opening. For offset configurations, contact us with your specifications for a custom quote.