Fuel pump size calculator
Find the Flow You Need
How it works
Calculating fuel pump size
This fuel pump size calculator helps you determine exactly how much fuel flow your engine needs based on horsepower, fuel type, and the specific induction setup you’re running. It uses real engineering math – BSFC, fuel density, rising-rate regulator behavior, and pressure-corrected flow – to estimate the minimum required pump output under actual operating conditions.
Whether you’re running EFI, carbureted NA, draw-through turbo, or blow-through boost, the calculator automatically applies the correct fuel pressure logic for your system. It also comes with a 10% built-in safety factor.
Just enter your power target and base pressure, and it will output the required flow in L/hr and GPH, along with the fuel system pressure your pump must support. This ensures you choose a pump that won’t starve the engine at full load, boost, or high RPM.
Interpreting the results
Required Fuel Pump Flow (L/hr & GPH)
This value represents the minimum amount of fuel your engine needs at full throttle, based on horsepower, BSFC, and fuel type.
Always select a pump that can exceed this flow at the pressure shown below, not just its advertised “free flow” rating.
Base Fuel Pressure (Bar / PSI)
This is the pressure your regulator or carb inlet is set to with no boost.
For EFI engines, this is typically 3.0–4.0 bar (43.5–58 psi).
For carbureted setups, it’s usually 0.25–0.5 bar (4–7 psi).
Boost Pressure (Bar / PSI)
Displayed only for boosted setups.
Boost does not increase fuel demand directly, but it does increase the pressure your fuel pump must work against for EFI and blow-through carb setups.
Total Fuel System Pressure (Bar / PSI)
This is the pressure your pump must sustain while still delivering the required flow.
EFI and blow-through systems add boost to the base pressure (1:1 rising–rate), while draw-through carb setups do not.
Always compare your pump’s flow chart to this value to ensure it can support the required L/hr at this pressure.
Rule of thumb:
If your pump selection is close, go up one size – pumps lose performance with heat, age, and voltage drop.
Fuel Pump Size Calculator
EFI & Carb blow-through: boost is added to base fuel pressure via a 1:1 reference.
Carb draw-through: boost does not change fuel pressure, only engine horsepower.
NA modes: boost is not used.
Results:
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