HVAC Duct Sizing Calculator

Calculate duct size, air velocity, and friction loss for HVAC ductwork design using equal friction method.

Required air volume flow.
L/s
Main duct: 8-12, Branch: 5-8 m/s.
m/s
Width if rectangular duct. 0 for round calculation.
mm
Design friction loss. Low velocity: 0.8, Medium: 1.2 Pa/m.
Pa/m

Results

Required Round Duct Diameter-mm
Required Rect Duct Height-mm
Actual Velocity-m/s
Equivalent Diameter-mm
References: ASHRAE Fundamentals; SMACNA Duct Design Manual