Fuel Pump Calculator
Size fuel pumps for any build with BSFC, headroom, and per-pump duty cycle factored in.
Fueling Inputs
Results
What is a Fuel Pump Calculator?
The Fuel Pump Calculator estimates the fuel mass-flow and volume-flow a pump (or set of pumps) must deliver to support a given horsepower target. It accounts for BSFC, fuel density, number of pumps, duty cycle, and desired safety margin.
Use it before buying pumps, injectors, controllers, or wiring upgrades to avoid fuel starvation at wide-open throttle.
Reference output from the Horsepower Calculator, balance efficiency with the BSFC Calculator, estimate fuel spend via the Gas Calculator, and confirm static ratio inputs through the Compression Ratio Calculator.
Best for:
- Forced-induction builds - Ensure new turbos or superchargers have adequate fueling at higher horsepower levels.
- E85 conversions - Account for higher BSFC on ethanol blends which require more flow than gasoline.
- Dual-pump hangers - Size each pump correctly when splitting flow between multiple units.
- Diesel performance - Plan lift pump upgrades for high-horsepower diesels using their lower BSFC.
How the Fuel Pump Calculator Works
The tool multiplies horsepower by BSFC to get fuel mass flow (lb/hr). It then adjusts for safety headroom and divides by fuel density to convert to gallons per hour (GPH) and liters per hour (LPH).
Dividing by pump count and the duty-cycle limit tells you how much flow each pump must support without running at 100%.
- Fuel density defaults: gasoline 6.17 lb/gal, E85 6.6 lb/gal, diesel 7.1 lb/gal.
- Duty cycle represents the maximum percentage you want each pump to work at (e.g., 80%).
- Headroom covers future power adders or hot-fuel conditions.
Key Concepts Explained
BSFC (lb/hp/hr)
Higher BSFC means the engine burns more fuel per horsepower, increasing pump size.
Fuel density
Heavier fuels like diesel require less volume flow for the same mass flow.
Duty cycle
Operating pumps below 90% duty extends life and keeps voltage overhead for emergencies.
Headroom
Extra capacity prevents lean conditions as filters clog or when boost creeps beyond expectations.
How to Use This Calculator
Enter horsepower goal
Use crank or wheel horsepower; just remain consistent with BSFC values.
Set BSFC & fuel type
Choose a realistic BSFC for your tune and pick the matching fuel density.
Add pumps & duty cycle
Enter how many pumps you plan to run and the duty cap from your controller.
Review required flow
Use the LPH/GPH outputs to select pumps that meet or exceed per-pump requirements.
Benefits of Using This Fuel Pump Calculator
- • Prevent lean conditions – Size pumps accurately before the tune to keep AFR safe.
- • Budget smarter – Avoid over-buying expensive pumps or under-buying units that will fail early.
- • Upgrade planning – Quickly see if current pumps can handle a future horsepower goal.
- • Fuel-type flexibility – Compare gasoline vs E85 requirements instantly.
Factors That Affect Your Results
- • Fuel temperature – Hot fuel is less dense, reducing pump output.
- • Voltage drop – Long wiring runs or weak alternators can cut pump performance.
- • Filter restrictions – Dirty filters and regulators lower effective flow.
- • Boosted fuel pressure – Rising-rate regulators increase required flow at high boost.
Frequently Asked Questions
What inputs determine fuel pump size?
Horsepower target, brake specific fuel consumption (BSFC), fuel type density, desired safety headroom, number of pumps, and the duty cycle you want each pump to operate at.
What is BSFC?
Brake specific fuel consumption measures pounds of fuel burned per horsepower per hour. Typical values: 0.50 for gasoline, 0.65 for E85, 0.40 for diesel.
Why add headroom above the calculated flow?
Headroom ensures pumps are not maxed out on hot days, clogged filters, or future horsepower upgrades. Most builders add 10-30% extra capacity.
How do multiple pumps affect requirements?
The calculator divides total flow by the number of pumps and the duty cycle you plan to run. Two pumps at 80% duty can share the workload instead of one pump at 100%.
Does system voltage matter?
Higher voltage controllers can increase pump output, but this calculator focuses on fuel mass flow. Always check your pump's voltage vs flow chart.