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Calcimator

Hydraulic Motor Selection Calculator

Calculate hydraulic motor displacement, flow, torque, and power from speed and load requirements.

Inputs

%
%

Results

Motor displacement (in³/rev)

5

Calculated displacement (in³/rev)4.33
Required flow (GPM)11.76
Actual torque (ft·lb)173.1
Actual speed (RPM)500
Output power (HP)16.48
Input power (HP)20.59
Overall efficiency (%)80
Output Kw12.29
Drain Flow Gpm0.94
How to Use This Calculator
  1. Enter Required torque (ft·lb), Required speed (RPM), and System pressure (PSI).
  2. Set Back pressure (PSI), Mechanical efficiency, and Volumetric efficiency.
  3. Adjust Available flow (GPM, 0=unlimited) as needed.
  4. Review the Motor displacement (in³/rev) result.
  5. Use Calculated displacement (in³/rev) and Required flow (GPM) to inform your decision.

How the result changes with Required torque (ft·lb)

Required torque (ft·lb)Motor displacement (in³/rev)
5,000145
17,500510
32,500940
45,0001,300

What each input means

Required torque (ft·lb)
Continuous output torque needed at the motor shaft.
Required speed (RPM)
Desired motor output shaft speed.
System pressure (PSI)
Pump supply pressure available at the motor inlet.
Back pressure (PSI)
Pressure at the motor outlet (return line back pressure).
Mechanical efficiency
Motor mechanical (torque) efficiency (85-95% typical).
Volumetric efficiency
Motor volumetric (speed) efficiency (88-97% typical).
Available flow (GPM, 0=unlimited)
If pump flow is limited, enter available GPM (0 = no limit).

What each result means

Motor displacement (in³/rev)
Next standard motor displacement meeting torque requirement.
Calculated displacement (in³/rev)
Exact displacement needed from torque and pressure.
Required flow (GPM)
Flow needed to achieve desired RPM with the selected motor.
Actual torque (ft·lb)
Output torque with the selected motor displacement.
Actual speed (RPM)
Shaft speed (may be lower if flow is limited).
Output power (HP)
Mechanical power at the motor shaft.
Input power (HP)
Hydraulic power consumed (PSI × GPM / 1714).
Overall efficiency (%)
Mechanical × volumetric efficiency.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Required torque (ft·lb) = 150, Required speed (RPM) = 500, System pressure (PSI) = 3000, Back pressure (PSI) = 100 = 7 input(s) provided
  2. Calculate Motor displacement
    Motor displacement
    5 = 5
  3. Calculate Calculated displacement
    Calculated displacement = (requiredTorqueFtLb * 2 * π * 12) / (deltaPsi * mechEff)
    4.33 = 4.33
  4. Calculate Required flow
    Required flow = (requiredRpm * selectedDisplacement) / (231 * volEff)
    11.76 = 11.76

Engine last updated . Checked against 3 independently-derived tests — how we verify calculators.

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