Residential HVAC Duct Sizing

Best practices for sizing ducts in home HVAC systems

Home HVAC systems require careful duct sizing to ensure comfort, efficiency, and quiet operation. Unlike commercial systems, residential ducts prioritize low noise levels over maximum airflow capacity.

A typical home layout showing main trunk, branches, and register locations with CFM requirements

Alternative layout with centrally located HVAC unit and dual trunks serving each side of the home

Key Principles for Home Duct Sizing

Keep velocities low (600-900 FPM for supply mains) to minimize noise
Use lower friction rates (0.06-0.10 in.wg/100ft) for quieter operation
Size return ducts 10-15% larger than supply ducts for the same CFM

Typical Residential Duct Sizes

Duct Location	CFM	Round Duct	Velocity
Main trunk	800-1200	12-14"	700-900 FPM
Branch ducts	100-400	6-8"	600-800 FPM
Runouts to registers	50-150	4-6"	400-600 FPM

Try this example →

Common Residential Mistakes

Warning

Using undersized ducts to save money (causes noise and poor airflow)
Running excessively long flex duct runs (increases friction dramatically)
Not accounting for register restrictions (size register for 500 FPM or less)

Sources

Try the Calculator

Use our duct calculator with residential settings to size your home HVAC ducts correctly.

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