RV Vent Fan CFM Calculator
Roof vent fan size for an RV or van.
Enter your values
Enter the interior length in ft.
Enter the interior width in ft.
Enter the interior height in ft.
Enter the air changes in ACH.
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.
- Fan airflow
- 324 CFM
- Interior volume
- 432 cu ft
- Intake opening needed
- 1.08 sq ft
- Cooking boost (60 ACH)
- 432 CFM
- Power draw estimate
- 16.2 W
Quick answer
A camper interior is small, so most van builds target 30-60 air changes per hour for effective cooling.
CFM = interior volume x ACH / 60
At a glance
| What it does | Roof vent fan size for an RV or van. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Interior length, Interior width, Interior height, Air changes |
| Main output | Fan airflow |
| Formula | CFM = interior volume x ACH / 60 |
| Cost | Free — no sign-up, no download |
How to use the RV Vent Fan CFM Calculator
- 1Measure the usable interior box dimensions.
- 2Pick 30-45 ACH for comfort, more if you cook inside a lot.
- 3Crack a window or fit a floor vent so the fan has intake air.
Inputs explained
- Interior length(ft)
- Enter the interior length in ft.
- Interior width(ft)
- Enter the interior width in ft.
- Interior height(ft)
- Enter the interior height in ft.
- Air changes(ACH)
- Enter the air changes in ACH.
Worked example
Using the values the calculator loads with:
Inputs
- Interior length12 ft
- Interior width6 ft
- Interior height6 ft
- Air changes45 ACH
Results
- Fan airflow324 CFM
- Interior volume432 cu ft
- Intake opening needed1.08 sq ft
- Cooking boost (60 ACH)432 CFM
- Power draw estimate16.2 W
Frequently asked questions
One fan or two?
Two fans, one intake and one exhaust, cross-ventilate far better than a single unit.
Battery drain?
Most 12V roof fans use 1-3 amps, so overnight running is easy on a modest battery bank.
What do I need to enter into the RV Vent Fan CFM Calculator?
Just 4 values: interior length, interior width, interior height, air changes. 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 RV Vent Fan CFM Calculator work out the answer?
A camper interior is small, so most van builds target 30-60 air changes per hour for effective cooling. It applies the formula CFM = interior volume x ACH / 60 and shows the working so you can check each step by hand.
Is the RV Vent Fan CFM 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.