Garage Exhaust Fan Sizing Calculator
Exhaust fan CFM for a residential garage.
Enter your values
ⓘ Live results
Results
- Required fan airflow
- 1,188 CFM
- Garage volume
- 4,752 cu ft
- Equivalent ACH
- 15
- Wall fan size
- 2,000 CFM model
Quick answer
A residential garage exhaust fan is typically sized to turn over the garage air in 3-5 minutes, or about 12-20 air changes per hour.
CFM = volume / turnover minutes
How to use the Garage Exhaust Fan Sizing Calculator
- 1Measure the garage length, width and ceiling height.
- 2Pick a turnover time — 3-5 minutes is typical for clearing vehicle exhaust or fumes.
- 3Choose an off-the-shelf fan at or above the calculated CFM.
Worked example
Using the values the calculator loads with:
Inputs
- Garage length22 ft
- Garage width24 ft
- Ceiling height9 ft
- Turnover time4 minutes
Results
- Required fan airflow1,188 CFM
- Garage volume4,752 cu ft
- Equivalent ACH15
- Wall fan size2,000 CFM model
Frequently asked questions
Do I need makeup air?
Yes, crack a window or door, or add a passive intake louvre sized similarly to the fan opening.
Should it run on a timer?
A timer or CO sensor interlock is ideal so the fan runs only when needed.
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.