Fuel Pump Calculator

Multiply horsepower by brake-specific fuel consumption (BSFC) to get fuel flow in pounds per hour, then add a safety margin. A 300 hp naturally aspirated engine at 0.50 lb/hp/hr BSFC needs 150 lb/hr at the crank, or 180 lb/hr with a 20 percent margin, about 110 litres per hour.

Brake-specific fuel consumption (BSFC) is the mass of fuel an engine burns per unit of power output per hour, typically in pounds per horsepower-hour. It directly scales the fuel flow calculation, a higher BSFC (common in forced-induction or rich-tuned engines) requires proportionally more pump capacity for the same horsepower.

Naturally aspirated gasoline engines typically run 0.45 to 0.55 lb/hp/hr. Turbocharged or supercharged engines often run 0.55 to 0.65 lb/hp/hr due to richer tuning for detonation control. E85 and methanol setups run higher still, often 0.70 to 0.80 lb/hp/hr, because of their lower energy density per gallon.

A safety margin accounts for voltage drop at the pump under load, fuel line and filter restriction, injector duty cycle limits, and future tune changes. Running a pump near 100% of its rated capacity also drops delivered fuel pressure, so sizing 15 to 25 percent above the calculated minimum keeps the pump in its efficient operating range.

LPH stands for litres per hour, the most common flow rate specification printed on aftermarket fuel pumps. This calculator converts your calculated lb/hr requirement into LPH so you can directly compare it against a pump's rated spec.

Usually yes. E85 has roughly 30 percent lower energy density than gasoline, so an engine needs proportionally more fuel volume to produce the same power, which is reflected in a higher BSFC input and a correspondingly higher required flow rate in this calculator.

A modestly oversized pump is normal and safe, since flow is regulated by the fuel pressure regulator or ECU. A massively oversized pump can generate more heat in the tank at low demand and adds unnecessary cost, but it is generally far less risky than undersizing, which can cause fuel starvation and lean conditions under load.

Turbocharged and supercharged engines typically run richer air-fuel ratios for detonation protection under boost, raising BSFC compared to a naturally aspirated engine of similar horsepower. Select the turbo/supercharged BSFC preset, or a custom higher value, to size the pump correctly.

Use crank horsepower (flywheel output) for fuel pump sizing, since BSFC figures are defined relative to brake (crank) power. Wheel horsepower is lower due to drivetrain losses and would undersize the pump if used directly.

Yes. An undersized pump cannot supply enough fuel volume at high RPM and load, causing the fuel pressure to drop, the mixture to run lean, and risking detonation or engine damage. Always size the pump using your target horsepower and appropriate BSFC, with a safety margin included.