Hydraulic Pump Shaft Power Calculator

Introduction

For mechanical design engineers sizing the electric motor or diesel engine on a hydraulic power unit — enter the flow and pressure the circuit needs and get the shaft power the prime mover must actually deliver once volumetric and mechanical losses are accounted for. This tool calculates required prime mover shaft power using the standard equation P(kW) = (Q * p) / (600 * total efficiency).

How To Use This Calculator

1. Enter the pump's flow rate in L/min.
2. Enter the working pressure in bar.
3. Enter the volumetric efficiency as a percentage (default 92).
4. Enter the mechanical efficiency as a percentage (default 90).
5. Read the required shaft power in kW, plus the substituted formula line, and use the reset link to start a new sizing case.

FAQ

Q: What equation converts hydraulic flow and pressure into pump shaft power?

A: P(kW) = (Q × p) / (600 × η_total), with Q in L/min, p in bar and η_total the combined pump efficiency — here the tool multiplies volumetric and mechanical efficiency to get η_total before dividing.

Q: How do volumetric and mechanical efficiency combine into total efficiency?

A: They multiply: η_total = η_vol × η_mech, so 92 % volumetric and 90 % mechanical give 0.92 × 0.90 = 0.828, or 82.8 % — and the shaft power is divided by that single figure.

Q: Why is the constant 600 in the hydraulic power formula?

A: 600 is the conversion constant in the standard form P(kW) = (Q × p) / (600 × η_total) when flow is in L/min and pressure in bar; the same arithmetic without efficiencies, Q × p / 600, is the hydraulic power the tool shows as an intermediate value.

Q: Is this shaft power figure accurate enough to order a motor?

A: It is for preliminary estimation only and is not a substitute for review by a qualified or licensed engineer — the calculation accounts for the two efficiencies you enter, nothing else, so losses in couplings, controls and the rest of the circuit are not included.