Fuel Pump Size Calculator
Find the pump flow your power target needs in litres per hour, with the margin real fuel systems require.
Your build
- Published pump ratings are usually measured at 13.5 volts and low pressure. Real flow at boost pressure is substantially lower.
- Voltage matters as much as pressure. A pump on a tired wiring harness can lose 15% of its flow.
- The return line, filter and feed line all restrict flow. A big pump through a stock line is still a stock fuel system.
From horsepower to litres per hour
Power sets fuel mass flow through BSFC, and fuel density converts that mass into volume. 500 naturally aspirated horsepower burns roughly 250 pounds of gasoline an hour, which is about 41 gallons, or 156 litres.
Then you add margin, because a pump rated at 255 LPH does not deliver 255 LPH in your car.
Ratings are measured in ideal conditions
Pump flow figures are typically quoted at 13.5 volts and low outlet pressure. Raise the pressure to what a boosted engine actually runs and flow drops noticeably. Drop the voltage to what a tired harness delivers and it drops again.
Between those two effects a 255 LPH pump can be delivering closer to 180 LPH where it matters. That is what the safety margin is covering.
The pump is not the whole system
Feed line diameter, filter restriction, return line size and the regulator all limit what reaches the injectors. Fitting a large pump to stock lines moves the bottleneck rather than removing it. Wiring matters too, since a big pump on a stock circuit will be voltage starved exactly when it is working hardest.
Frequently asked questions
What size fuel pump do I need for 500 hp?
Naturally aspirated on gasoline, around 195 LPH including a 25% margin. Boosted on gasoline, closer to 240 LPH. On E85 the same 500 hp needs over 300 LPH because ethanol carries less energy per unit volume.
Is a 255 LPH pump enough for my build?
It depends on pressure and fuel. A 255 LPH pump at low pressure on gasoline supports around 600 naturally aspirated horsepower with margin. Run it at 60 psi on a boosted engine and real flow may be closer to 190 LPH, which supports considerably less.
Do I need to upgrade fuel lines with the pump?
Often yes. Stock feed lines are sized for stock power, and a restriction upstream of the pump is worse than one downstream because it causes cavitation. Check line size, filter capacity and the return path together with the pump.
Should I run dual pumps or one big one?
One correctly sized pump is simpler and more reliable. Dual pumps make sense when a single pump cannot supply the flow, or when you want a staged setup where the second pump only runs under boost to keep the fuel cooler and reduce load at idle.
Everything on this page is an estimate worked out from the numbers you entered and typical figures for the conditions you picked. Your vehicle, your parts and your conditions will differ. Check anything you intend to act on against the manufacturer's specification, the service manual, or a qualified technician. Verifying the result before relying on it is up to you.