Duct Shape Converter
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The cross-sectional Area of a duct is a determining factor in duct sizing for how much airflow the duct is designed for at a specific allowable friction or noise level.
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A rectangular duct of a certain width and height can be equated with an equivalent round duct of diameter where both shapes of ducts share the same cross-sectional area.
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Similarly, a round duct of a specific diameter can be equated with an equivalent rectangular duct of which the combination of width and height gives the same cross-sectional area as that of the round duct.
The formula for the computation of rectangular and round duct size:
![Capture1.JPG](https://static.wixstatic.com/media/17b446_59f379b853464c3790810981dd59cf1c~mv2.jpg/v1/fill/w_600,h_320,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Capture1_JPG.jpg)
Equating the formulae for rectangular and round duct’s size:
![Capture2.JPG](https://static.wixstatic.com/media/17b446_ede5208712bc4428a9c48d4881799c92~mv2.jpg/v1/fill/w_419,h_338,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Capture2_JPG.jpg)
![Capture3.JPG](https://static.wixstatic.com/media/17b446_d3c76c58c0de4733b4fb5219d9f9cd2a~mv2.jpg/v1/fill/w_474,h_330,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/Capture3_JPG.jpg)
A downloadable Excel File for Rectangular to Round / Round to Rectangular Duct Converter is available below.
Duct Converter (Excel)
Toward the end of the calculator, the Aspect Ratio of a duct is the Ratio of Width to Height or Height to Width (longer side to shorter side) of a Rectangular Duct. To calculate Total Duct Surface Area based on a duct's dimension and aspect ratio, refer to the page Rectangular Duct Aspect Ratio Calculator.
![300 x 600 px Ads hd1.jpg](https://static.wixstatic.com/media/17b446_70300bd537ed457e82fe633047bd2616~mv2.jpg/v1/fill/w_60,h_120,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/300%20x%20600%20px%20Ads%20hd1.jpg)