Garage Ventilation CFM Calculator
Exhaust fan size for a garage or workshop.
Enter your values
ⓘ Live results
Results
- Exhaust fan size
- 500 CFM
- Air changes used
- 6 ACH
- Garage volume
- 4,752 cu ft
- Intake opening needed
- 137 sq in
Quick answer
Garages usually need 6–12 air changes per hour, rising to 20 or more where engines run or solvents are used.
CFM = garage volume x ACH / 60
How to use the Garage Ventilation CFM Calculator
- 1Measure the garage and enter the dimensions.
- 2Pick the use case — running engines demand far more air.
- 3Fit the exhaust high and the intake low on the opposite wall.
Worked example
Using the values the calculator loads with:
Inputs
- Garage length24 ft
- Garage width22 ft
- Ceiling height9 ft
- Main useParking and storage
Results
- Exhaust fan size500 CFM
- Air changes used6 ACH
- Garage volume4,752 cu ft
- Intake opening needed137 sq in
Frequently asked questions
Is a window enough?
Not when engines run. Carbon monoxide needs mechanical extraction with make-up air.
Where should the fan go?
High on the wall furthest from the intake so air sweeps across the whole space.
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.