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Port Velocity Calculator
Calculate intake port velocity from flow and area
Port velocity is the speed of the air charge through the intake port, found by dividing airflow by the port's cross-sectional area.
Formula: Velocity (fps) = CFM × 2.4 ÷ cross-sectional area (in²)
What this number means
This calculates air velocity through an intake port from flow in CFM and the port's cross-sectional area. Velocity, not flow alone, is what fills cylinders and makes torque — a port can flow big numbers and still be lazy if it is too large.
What to change next
If velocity is low for the engine's size and RPM, a smaller, efficient port usually drives better than a bigger one. If velocity is extremely high at your shift point, the port is likely choking and costing top-end power.
Worked example
260 CFM through a 2.2 sq in port gives a port velocity of ≈ 283 ft/sec.