CFM to Horsepower Calculator
Estimate horsepower from airflow in CFM, and size a carburetor or intake.
Because an engine's power is limited by how much air it can flow, airflow in CFM gives a good estimate of supported horsepower. This calculator helps you match a carburetor or intake to a power target.
CFM to HP Formula
This estimates the horsepower the induction can support, not what the engine will necessarily make — actual power also needs matching displacement, compression, cam, fuel, and tune. It's most useful for sizing carbs, throttle bodies, and intakes.
How to Use This Calculator
- Enter airflow in CFM (e.g. carburetor rating).
- Read the supported horsepower.
Worked Example
Frequently Asked Questions
A naturally aspirated engine supports roughly 1.6 horsepower per CFM of airflow, so multiply CFM by about 1.6 for a rough capacity estimate.
No. Oversizing the carb or intake beyond the engine's airflow needs hurts throttle response and low-end power without adding top-end.
It estimates the horsepower the airflow (e.g. a carburetor's CFM rating) can support. The engine must also be built to use it.
No. Forced induction supplies far more air per unit of displacement, so the naturally aspirated CFM-to-HP rule doesn't apply directly.
Estimate airflow from displacement, RPM, and volumetric efficiency, then choose induction that meets or slightly exceeds that figure.