Radiator Fan CFM Calculator
Electric cooling fan sizing for an engine.
Enter your values
Enter the engine horsepower in HP.
Choose one of: Naturally aspirated, Turbo / supercharged.
Enter the radiator width in in.
Enter the radiator height in in.
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 needed
- 963 CFM
- Core face area
- 3.17 sq ft
- Face velocity
- 304 FPM
- Shroud
- Cover 70%+ of the core
- Current draw estimate
- 5.3 A at 12V
Quick answer
A common rule is 250-300 CFM of radiator airflow per 100 horsepower, with more for forced induction.
CFM ≈ HP x 2.75 x boost factor
At a glance
| What it does | Electric cooling fan sizing for an engine. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Engine horsepower, Aspiration, Radiator width, Radiator height |
| Main output | Fan airflow needed |
| Formula | CFM ≈ HP x 2.75 x boost factor |
| Cost | Free — no sign-up, no download |
How to use the Radiator Fan CFM Calculator
- 1Enter crank horsepower and whether the engine is boosted.
- 2Measure the radiator core, not the tanks.
- 3Fit a full shroud — an unshrouded fan pulls air from the easiest path, not through the core.
Inputs explained
- Engine horsepower(HP)
- Enter the engine horsepower in HP.
- Aspiration
- Choose one of: Naturally aspirated, Turbo / supercharged.
- Radiator width(in)
- Enter the radiator width in in.
- Radiator height(in)
- Enter the radiator height in in.
Worked example
Using the values the calculator loads with:
Inputs
- Engine horsepower350 HP
- AspirationNaturally aspirated
- Radiator width24 in
- Radiator height19 in
Results
- Fan airflow needed963 CFM
- Core face area3.17 sq ft
- Face velocity304 FPM
- ShroudCover 70%+ of the core
- Current draw estimate5.3 A at 12V
Frequently asked questions
Push or pull?
A puller fan behind the radiator is roughly 15-20% more effective than a pusher in front.
Two fans?
Dual fans give redundancy and better core coverage on wide radiators.
What do I need to enter into the Radiator Fan CFM Calculator?
Just 4 values: engine horsepower, aspiration, radiator width, radiator height. 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 Radiator Fan CFM Calculator work out the answer?
A common rule is 250-300 CFM of radiator airflow per 100 horsepower, with more for forced induction. It applies the formula CFM ≈ HP x 2.75 x boost factor and shows the working so you can check each step by hand.
Is the Radiator 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.