Transfer Grille Size Calculator
Size a transfer grille for a closed-door room.
Enter your values
ⓘ Live results
Results
- Required free area
- 0.4 sq ft
- Gross grille size
- 0.571 sq ft
- Approx square size
- 9.1 x 9.1 in
Quick answer
Transfer grilles are sized for low velocity, typically 200-300 FPM, since low noise matters more than compact size in a wall opening.
Free area = supply CFM / transfer velocity
How to use the Transfer Grille Size Calculator
- 1Enter the CFM being supplied to the closed-door room.
- 2Use 200-300 FPM for a quiet transfer path.
- 3Size the grille's gross opening from its free-area fraction.
Worked example
Using the values the calculator loads with:
Inputs
- Room supply CFM100 CFM
- Transfer velocity250 FPM
- Free area fraction70 %
Results
- Required free area0.4 sq ft
- Gross grille size0.571 sq ft
- Approx square size9.1 x 9.1 in
Frequently asked questions
Transfer grille vs jumper duct?
A transfer grille passes air directly through the wall, while a jumper duct routes it over the top of the wall through the attic or ceiling space.
Do transfer grilles block sound?
Standard transfer grilles pass sound easily; acoustically lined versions or offset ducted transfers reduce noise transfer.
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.