Typical Air Velocities: Main ducts: 1000-1800 FPM - Branch ducts: 800-1400 FPM - Supply outlets: 500-750 FPM - Return air: 800-1000 FPM
Typical Friction Rates: Low velocity: 0.05-0.08 - Standard: 0.1 - High velocity: 0.15-0.2 in.w.g./100ft
ASHRAE Design Guidelines: Aspect ratios greater than 4:1 not recommended
This HVAC ductulator performs instant duct sizing calculations using industry-standard ASHRAE formulas. Simply enter your CFM requirements and choose between friction-based or velocity-based sizing methods. Our calculator handles both round and rectangular ducts with automatic equivalent diameter calculations.
This ductwork CFM calculator simplifies air duct sizing for any HVAC project. Calculate air flow requirements, size ductwork properly, and ensure optimal CFM distribution throughout your system.
Get CFM calculations and duct sizes immediately with professional accuracy
All calculations follow ASHRAE guidelines and Huebscher equivalent diameter formulas
Calculate by friction rate or air velocity - perfect for any HVAC design approach
Supports both round and rectangular ducts with automatic equivalent sizing