What is a good duct velocity for home HVAC?

Heating & HVACSMACNA / ASHRAE Acoustics

Duct Airflow Velocity Calculator (CFM & FPM)

Calculate air velocity in Feet Per Minute (FPM) from CFM and duct cross-sectional area to prevent loud whistling and turbulent airflow noise.

Heating & HVAC Field StandardsSMACNA / ASHRAE Acoustics

Engineering formulations calibrated to IPC, UPC & NEC specificationsSub-Zero Cold Climate Tolerances

Quick Summary & Key Answer

Duct velocity in Feet Per Minute (FPM) is calculated by dividing airflow volume (CFM) by the duct's cross-sectional area in square feet: FPM = CFM / Area. For quiet residential performance, air velocity should remain between 700 and 900 FPM in branch ducts and below 1,200 FPM in main supply trunks.

Velocities above 1,200 FPM generate audible rushing noise and grille whistling.
Round ductwork has 20% less surface friction than equivalent-area rectangular duct.
1 FPM = 0.00508 meters per second.

Interactive Calculator

Adjust inputs for real-time results

Airflow VolumeCFM

CFM

Duct Shape

Duct Width or Round Diameterinches

inches

Duct Height (if rectangular)inches

inches

Calculated OutputStandard Trunk (900-1200 FPM)

Air Velocity (Feet Per Minute)

1029 FPMFPM

Duct Cross-Sectional Area: 0.78 sq ft
Air Velocity in Meters/Sec: 5.23 m/s
Velocity Pressure (Pv): 0.066 in w.g.

Note: ASHRAE recommends keeping residential branch ducts under 700-900 FPM and main trunks under 1,000-1,200 FPM to prevent objectionable duct rumble.

ASHRAE Recommended Duct Velocities

Keeping air velocity within design limits reduces static pressure drop, lowering blower motor electrical consumption.

Frequently Asked Questions

Common questions regarding this calculation and code compliance

Between 700 and 900 FPM for branch run-outs, and 1,000 to 1,200 FPM for main plenum trunks.