Register Face Velocity Calculator
Grille face velocity and noise check.
Enter your values
ⓘ Live results
Results
- Face velocity
- 320 FPM
- Free area
- 0.375 sq ft
- Noise check
- Quiet
- Throw estimate
- 3.2 ft
Quick answer
Register face velocity is airflow divided by the grille's free area, which is usually 70-80% of the nominal size.
FPM = CFM / (nominal area x free area factor)
How to use the Register Face Velocity Calculator
- 1Enter the airflow that register should deliver.
- 2Enter its nominal size and the manufacturer's free area percentage.
- 3Keep bedrooms under about 500 FPM.
Worked example
Using the values the calculator loads with:
Inputs
- Airflow120 CFM
- Grille width12 in
- Grille height6 in
- Free area75 %
Results
- Face velocity320 FPM
- Free area0.375 sq ft
- Noise checkQuiet
- Throw estimate3.2 ft
Frequently asked questions
Bedroom vs living room?
Bedrooms should stay quieter — target 400-500 FPM; living areas tolerate 600-700.
Return grilles?
Sizing returns at 300-400 FPM keeps them silent.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.