Duct Sizer
Size ductwork using ASHRAE equal friction or velocity methods
Based on ASHRAE Fundamentals (Darcy-Weisbach with hydraulic diameter)
About This Calculator
This duct sizer uses the Darcy-Weisbach equation with hydraulic diameter for friction calculations, matching the methodology used by professional tools like Revit MEP.
Equal Friction Method: Sizes duct to maintain a constant friction rate (typically 0.08 in.wg/100ft for low-velocity systems).
Velocity Method: Sizes duct to not exceed a maximum velocity (typically 2000 FPM for supply air).