Radiator Fan CFM Calculator
Electric cooling fan sizing for an engine.
Enter your values
ⓘ Live results
Results
- 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
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.
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.
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.