Hydraulic Pump Flow Rate Calculator

Log Splitter Calculators

How to calculate a hydraulic pump fluid flow rate

To find the output flow rate of a hydraulic pump, use this pump flow formula:

Flow (GPM) = (RPM x Disp) / 231
RPM = Rotations Per Minute
Disp = Pump Displacement in Cubic Inches
GPM = Gallons Per Minute

Hydraulic Pump Displacement Formula:

Revolutions Per Minute (RPM) x Displacement in³÷ 231 = gpm

Example: The output flow rate of a pump spinning at a rate of 1500rpm with a displacement of 2.75 cubic inches:

Flow (GPM) = (1500 x 2.75 = 4,125 ÷ 231 = 17.85

Calculated out this gives an output flow of 17.85 GPM

Pump Output Flow (in Gallons Per Minute)

RPM x Pump Displacement ÷ 231

How much oil flow will be produced by a 2.50 cubic inch pump operating at 1100 rpm? 1100 x 2.50 = 2750 ÷ 231 = 11.90 GPM

Pump Displacement Needed for GPM of Output Flow

231 x GPM ÷ RPM

Displacement needed to produce 8 gpm at 1540 rpm?

231 X 7 ÷ 1740 = 0.93 cubic inches per revolution

There are three categories of efficiency used to describe hydraulic pumps (and motors).

Volumetric efficiency
Mechanical/hydraulic efficiency
Overall efficiency

Volumetric efficiency is determined by dividing the actual flow delivered by a pump at a given pressure by its theoretical flow. Theoretical flow is calculated by multiplying the pump's displacement per revolution by its driven speed.

Mechanical/hydraulic efficiency is determined by dividing the theoretical torque required to drive it by the actual torque required to drive it.

Overall efficiency is simply the product of volumetric and mechanical/hydraulic efficiency. Overall efficiency is used to calculate the drive power required by a pump at a given flow and pressure.

Log Splitter Hydraulic Circuit Schematic