Fuel Injector Flow Rate Calculator

Calculate the required injector size based on engine power, number of cylinders, and other parameters.

Reviewed August 29, 2026 · Calculation methodology · Inputs stay in your browser

Engine Horsepower Enter your target horsepower output.

Number of Cylinders Enter the number of cylinders in your engine.

BSFC (Brake Specific Fuel Consumption) Typical values: 0.4-0.5 for naturally aspirated, 0.55-0.65 for forced induction.

Maximum Duty Cycle (%) Recommended safe maximum is 80% to maintain injector linearity.

Number of Injectors Usually the same as the number of cylinders.

Flow Rate Value Enter the flow rate value you want to convert.

From Unit Select the original unit of your flow rate.

Fuel Injector Tips

Always size injectors for your maximum expected power output plus a safety margin.
Most stock engines use a duty cycle of 80% or less to maintain injector linearity.
Higher BSFC values should be used for forced induction engines (turbo/supercharged).
When converting between lb/hr and cc/min, the specific gravity of fuel matters. The standard conversion uses 0.73 for gasoline.
Common stock injector sizes for 4-cylinder engines are 220-250cc/min, while performance applications often use 440-550cc/min.
Remember to match injector impedance (high or low) to your engine management system.