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Hydraulic Pump Flow Calculator

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

About Hydraulic Pump Flow Calculator

A positive displacement pump moves its displacement once per revolution, so theoretical flow is displacement times speed divided by 231 cubic inches per gallon. Volumetric efficiency accounts for internal slip past clearances, which rises with pressure and with oil temperature as viscosity falls.

Formula

Pump flow

GPM = displacement in³/rev x rpm / 231 x volumetric efficiency

Worked example

With the default values below, Hydraulic Pump Flow Calculator returns Delivered flow of 17.92. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pump displacementminimum 0.01 in³/rev
2.5 in³/rev
Drive speedminimum 1 rpm
1,800 rpm
Volumetric efficiencyaccepts 30–100 %
92 %

Results

Delivered flow
17.92 GPM
Theoretical flow
19.48 GPM
Delivered flow in litres
67.84 L/min
Internal leakage
1.558 GPM

Step by step

  1. 1Values used
  2. 2Pump flow
  3. 3Delivered flow= 17.92 GPM
  4. 4Theoretical flow= 19.48 GPM
  5. 5Delivered flow in litres= 67.84 L/min
  6. 6Internal leakage= 1.558 GPM

Assumptions and limits

  • The result is derived only from the 3 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 3 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

How is the Hydraulic Pump Flow figure worked out?

GPM = displacement in³/rev x rpm / 231 x volumetric efficiency. A positive displacement pump moves its displacement once per revolution, so theoretical flow is displacement times speed divided by 231 cubic inches per gallon.

Why does delivered flow fall as the pump wears?

Clearances open up, so more oil slips back internally at pressure. A drop in volumetric efficiency at rated pressure is the standard wear test for a hydraulic pump.

What values do I need to enter?

This calculator takes 3 inputs: Pump displacement, Drive speed, Volumetric efficiency. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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