Garage Exhaust Fan Sizing Calculator
Exhaust fan CFM for a residential garage.
Enter your values
Enter the garage length in ft.
Enter the garage width in ft.
Enter the ceiling height in ft.
Enter the turnover time in minutes.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Exhaust fan CFM for a residential garage. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Garage length, Garage width, Ceiling height, Turnover time |
| Main output | Required fan airflow |
| Formula | CFM = volume / turnover minutes |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Garage length(ft)
- Enter the garage length in ft.
- Garage width(ft)
- Enter the garage width in ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
- Turnover time(minutes)
- Enter the turnover time in minutes.
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.
What do I need to enter into the Garage Exhaust Fan Sizing Calculator?
Just 4 values: garage length, garage width, ceiling height, turnover time. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Garage Exhaust Fan Sizing Calculator work out the 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. It applies the formula CFM = volume / turnover minutes and shows the working so you can check each step by hand.
Is the Garage Exhaust Fan Sizing Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.