Duct Size Calculator 🌀

Calculate HVAC duct dimensions using velocity or equal friction method. Supports round and rectangular sizing per ASHRAE/SMACNA.

📊 Input Parameters

🌬️ Velocity Method

📐 Equal Friction

Airflow Rate *

Volume flow rate of air through the duct

Design Velocity

Main ducts: 1200-2000 FPM | Branches: 600-1200 FPM

Friction Rate

in.wg/100ft

Typical: 0.08-0.1 in.wg per 100ft

Aspect Ratio (W:H) for Rectangular

🌀

Enter airflow and velocity/friction rate,
then click "Calculate Duct Size"