Free Web Tool · ASHRAE Duct

Duct Sizing

Equal-friction duct sizing — round D and equivalent rectangular dimensions for an air flow Q at target friction Δp/L per ASHRAE.

Input

Results

Round diameter D
Velocity v
Velocity pressure
Equivalent rect. a × b
Reynolds Re
Method

For target Δp/L (Pa/m) at standard air, D ≈ 1.265·(Q^0.38)/(Δp/L)^0.176, with Q in m³/s. v = Q/A, A = πD²/4. Equivalent rectangular: De = 1.30·(a·b)^0.625 / (a+b)^0.25 — here aspect a=k·b given, solve b such that De ≈ D.