A fuel pump’s rated flow drops as the pressure it pushes against rises, so choose a pump that meets the flow at your running pressure – including boost on a return-style system with a 1:1 regulator – with a 20–30% safety margin.
How to use the Fuel Pump Calculator
- Target horsepower
- Induction
- Fuel
- Base fuel pressure
- Maximum boost
- Fuel system
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the target horsepower, induction type, fuel, base fuel pressure and maximum boost, and choose the fuel system type.
Tips
- Use your own measured figures – fuel economy, speed and prices vary a lot with driving style, traffic, load and season.
- Pick the unit in each field’s menu (miles or kilometres, mpg or L/100 km); the calculator converts everything for you.
- Fill up to the brim twice and divide the distance by the fuel added to measure real fuel economy.
- For vehicle modifications, treat results as a starting point and confirm with the parts maker or a professional mechanic.
Common mistakes to avoid
- Mixing US and imperial (UK) gallons – a UK gallon is about 20% bigger.
- Using the advertised fuel economy instead of real-world figures.
- Forgetting tolls, parking and wear and tear when comparing driving with public transport.
Inputs explained
| Field | What to enter |
|---|---|
| Target horsepower | In hp |
| Induction | Choose one: Naturally aspirated, Turbocharged, Supercharged |
| Fuel | Choose one: Petrol, E30, E85, Methanol |
| Base fuel pressure | Units: psi, bar, kPa |
| Maximum boost | Units: psi, bar, kPa |
| Fuel system | Choose one: Return (1:1 regulator), Returnless |
What each result means
- Required flow = [Target horsepower]×[Induction]×[Fuel]
- Flow with 25% safety margin = [Required flow]×1.25
- Pump must deliver it at = [Base fuel pressure] + [Fuel system]×[Maximum boost]
Example values
How the main result changes when Target horsepower changes and everything else stays at the example values above:
| Target horsepower (hp) | Required flow (L/h) |
|---|---|
| 225 | 93 |
| 337.5 | 140 |
| 450 | 187 |
| 562.5 | 233 |
| 675 | 280 |
| 900 | 374 |
Formula
Flow (L/h) ≈ hp × 0.3735 (naturally aspirated), × 0.415 (turbo), × 0.498 (supercharged)× fuel factor (E30 1.1, E85 1.4, methanol 2.2)Pump pressure = base pressure + boost (return system)Worked example
Inputs — Target horsepower: 450 hp; Induction: Turbocharged; Fuel: Petrol; Base fuel pressure: 43.5 psi; Maximum boost: 15 psi; Fuel system: Return (1:1 regulator).
Results — Required flow = 187 L/h; Flow with 25% safety margin = 233 L/h; Pump must deliver it at = 58.5 psi.
Frequently asked questions
What fuel pump do I need for 500 hp?
About 190–250 L/h for petrol depending on induction, delivered at your running pressure.
Why does boost raise the pressure requirement?
On a return system the regulator raises fuel pressure 1:1 with boost so injector flow stays consistent.
Do I need a bigger pump for E85?
Yes – about 30–40% more flow than petrol for the same power.
What formula does the Fuel Pump Calculator use?
Flow (L/h) ≈ hp × 0.3735 (naturally aspirated), × 0.415 (turbo), × 0.498 (supercharged).