Fuel Pump Calculator
Ensure your fuel system can support your horsepower goals by estimating fuel mass and volume flow needs for different fuels and pump configurations.
Higher BSFC values mean more fuel required per horsepower (forced induction ≈ 0.55–0.75).
Accounts for voltage drop, filters, and plumbing restrictions (typical 80–90%).
How to Use This Calculator
Enter target horsepower
Use crank horsepower for engine bay pumps or wheel horsepower with drivetrain loss adjustments.
Choose BSFC and fuel type
Higher BSFC values (0.60–0.75) apply to boosted engines. Select fuel to set density conversion.
Adjust system efficiency
Lower efficiency accounts for voltage drop or restrictive fittings. Most street cars use 80–90%.
Select pump count
Split total flow across parallel pumps. Useful for staged setups or redundant systems.
Formula
Fuel Flow (lb/hr) = (Horsepower × BSFC) ÷ (Efficiency ÷ 100)
Gallons per hour: Flow (lb/hr) ÷ Fuel Density (lb/gal)
Per pump: Total flow ÷ Number of pumps
Example: 600 hp on E85 (BSFC 0.65), 85% efficiency, two pumps:
Mass flow = (600 × 0.65) ÷ 0.85 = 458.8 lb/hr
Total flow = 458.8 ÷ 6.60 = 69.5 gph (263.2 L/h)
Per pump = 69.5 ÷ 2 = 34.8 gph (131.6 L/h)
About the Fuel Pump Calculator
An undersized fuel pump can lean out your engine and cause catastrophic damage. This calculator helps tuners, racers, and builders size pumps correctly for gasoline, E85, or diesel applications.
When to Use This Calculator
- Performance upgrades: Determine pump capacity when adding turbos, superchargers, or nitrous.
- Fuel system redesign: Size pumps for return-style conversions or ethanol conversions.
- Motorsport planning: Validate fuel delivery for endurance and drag racing builds.
- Diesel tuning: Ensure high-horsepower trucks have adequate lift pump capacity.
Why Use Our Calculator?
- ✅ Fuel-aware: Accounts for different fuel densities automatically.
- ✅ Efficiency factor: Realistic results that consider voltage drop and plumbing losses.
- ✅ Multi-pump support: Splits flow needs across staged or dual pump setups.
- ✅ Unit flexibility: Outputs both gph and L/h for US and international builders.
Common Applications
Street/strip cars: Prepare for E85 conversions or boost increases.
Marine engines: Ensure high-output boats maintain steady fuel supply.
Industrial engines: Size pumps for generators or agricultural machinery.
Tips for Best Results
- Include 15–25% overhead to keep pumps within safe duty cycles.
- Match pump ratings at your system pressure (PSI). Flow drops as pressure rises.
- Use dedicated wiring and relays to maintain voltage and efficiency.
- Pair with injector sizing tools to ensure the whole fuel system is balanced.
Frequently Asked Questions
How do I choose BSFC?
Naturally aspirated gasoline engines typically use 0.45–0.55 lb/hp·hr. Turbocharged or supercharged engines often require 0.60–0.75, and E85 setups trend higher due to lower energy density.
Does pump flow rating change with pressure?
Yes. Published flow numbers are usually at a specific pressure (e.g., 43.5 psi). Flow decreases as fuel pressure rises—consult manufacturer flow charts.
Can I run multiple pumps?
Absolutely. This calculator splits flow between pumps for staged, twin, or triple setups. Ensure wiring and relays handle combined current draw.
What safety margin should I target?
Aim for at least a 20% buffer over calculated needs to cover hot fuel, voltage drop, and future power increases.