Engine CFM Calculator
Calculate engine airflow in CFM (cubic feet per minute) from displacement, RPM, and volumetric efficiency.
How It Works
Enter engine displacement in cubic inches (or cc), target RPM, and volumetric efficiency percentage. The calculator determines airflow in CFM to help size carburetors, throttle bodies, and intake components.
Formula
CFM = (Displacement x RPM x VE) / (3456 x 2)
Frequently Asked Questions
What is volumetric efficiency?
Volumetric efficiency (VE) is the ratio of actual air drawn into the cylinder versus the theoretical maximum. Stock engines run 75-85% VE; well-tuned engines with good headers can exceed 100% VE at peak power RPM.
How do I use CFM to choose a carburetor?
Select a carburetor rated at or slightly above your calculated CFM at peak power RPM. Oversizing a carb hurts throttle response and fuel atomization; undersizing limits peak power.