Size round, rectangular, and flat oval HVAC ducts by CFM and velocity — with friction loss, equivalent diameter, pressure drop, noise ratings, and a full duct comparison table.
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Common HVAC duct scenarios
Recommended Size
Velocity Guidelines
Friction Guide
Target friction rate: 0.08–0.10 in.wg/100ft for residential.
Max friction: 0.15 in.wg/100ft for commercial.