Fuel Pump Flow Calculator

Work out fuel pump flow instantly with clear inputs, formula shown and shareable results.

About Fuel Pump Flow Calculator

Pump flow starts from the same BSFC calculation as injector sizing, converted from mass to volume by fuel density and increased by a safety margin. That margin matters because pump flow falls as fuel pressure rises and as voltage sags under load.

Formula

Fuel pump flow

mass flow = power x BSFC; volume flow = mass / density x (1 + margin)

Worked example

With the default values below, Fuel Pump Flow Calculator returns Pump flow required of 167.44. Change any input above and every figure here is recalculated in your browser.

Inputs used

Engine power: 400 hp
Brake specific fuel consumption: 0.55 lb/hp/h
Fuel density: 0.745 kg/L
Safety margin: 25 %

Results

Pump flow required: 167.44 L/h
Pump flow: 2.79 L/min
Fuel mass flow: 99.79 kg/h
Pump flow: 44.23 gal/h

Step by step

1Values used
2Fuel pump flow
3Pump flow required= 167.44 L/h
4Pump flow= 2.79 L/min
5Fuel mass flow= 99.79 kg/h
6Pump flow= 44.23 gal/h

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does pump flow drop at high pressure?

A pump's flow-pressure curve is falling. A pump rated 300 L/h free-flow might deliver only 200 L/h at 4 bar, so ratings must be read at working pressure.

Does voltage matter?

Considerably. Flow falls roughly with voltage, so a pump tested at 13.5 V delivers noticeably less at 12.0 V with poor wiring.