Calculate theoretical hydraulic output power, estimated pump input power, and estimated power loss from pressure differential, flow rate, and overall efficiency. This free Hydraulic Pump Power Calculator supports Metric and US Imperial units and displays results in kW and hp.
1. Hydraulic Pump Power Calculator
Enter the pressure differential, flow rate and overall efficiency. Choose Metric, Imperial or Dual Unit display, then calculate the hydraulic output power, estimated input power and estimated power loss.
Important: Input power and power loss are estimates based on the overall efficiency you enter. Confirm the efficiency definition and operating conditions against the equipment manufacturer's data.
2. How the Calculator Works
The calculator first determines the theoretical hydraulic power transferred by the fluid. It then divides that result by the entered overall efficiency to estimate the required input power. Estimated power loss is the difference between input power and hydraulic output power.
3. Hydraulic Pump Power Formulas
3.1. Hydraulic output power — Metric units
When pressure differential is in bar and flow rate is in litres per minute:
3.2. Estimated input power
Overall efficiency is entered as a decimal in the equation. For example, 85% is ηₒ = 0.85.
3.3. Estimated power loss
3.4. US Imperial formula
When pressure differential is in psi and flow rate is in US gallons per minute:
Then calculate estimated input power and loss using the same efficiency relationships:
3.5. Symbols and conversions
| Symbol | Meaning | Unit |
|---|---|---|
| Δp | Pressure differential | bar or psi |
| Q | Volumetric flow rate | L/min or US GPM |
| Pₕ | Theoretical hydraulic output power | kW or hp |
| Pᵢₙ | Estimated required input power | kW or hp |
| Pₗₒₛₛ | Estimated power loss | kW or hp |
| ηₒ | Overall efficiency as a decimal | 0 to 1 |
- 1 kW ≈ 1.341 hp.
- 1 hp ≈ 0.746 kW.
- 1 bar = 0.1 MPa ≈ 14.5038 psi.
- 1 US GPM ≈ 3.78541 L/min.
4. Worked Examples
4.1. Metric example
Given: pressure differential = 160 bar, flow rate = 80 L/min, overall efficiency = 85% (ηₒ = 0.85).
- Hydraulic output power: Pₕ = 160 × 80 / 600 = 21.33 kW.
- Estimated input power: Pᵢₙ = 21.33 / 0.85 ≈ 25.10 kW.
- Estimated power loss: Pₗₒₛₛ = 25.10 − 21.33 ≈ 3.77 kW.
Using unrounded intermediate values gives the displayed results to two decimal places.
4.2. Imperial example
Given: pressure differential = 2,320.6 psi, flow rate = 21.13 US GPM, overall efficiency = 85%.
- Hydraulic output power: Pₕ = 2,320.6 × 21.13 / 1714 ≈ 28.60 hp.
- Estimated input power: Pᵢₙ = 28.60 / 0.85 ≈ 33.65 hp.
- Estimated power loss: Pₗₒₛₛ = 33.65 − 28.60 ≈ 5.05 hp.
Small differences can occur because the example uses rounded unit conversions.
5. Metric and Imperial Reference
| Quantity | Metric | Imperial |
|---|---|---|
| Pressure differential | bar | psi |
| Flow rate | L/min | US GPM |
| Power | kW | hp |
| Efficiency | % or decimal | % or decimal |
6. Engineering Notes and Limitations
- Use pressure differential across the relevant component, not automatically the system's maximum pressure or pump pressure setting.
- Overall efficiency should represent the equipment and drive train covered by the estimate. Do not combine incompatible efficiency values or count the same loss twice.
- The calculated input power is an estimate. Actual electric motor input also depends on motor and drive efficiency if those are not included in the overall efficiency value.
- Power loss is estimated as input power minus hydraulic output power; it is not a detailed breakdown of heat, leakage, mechanical friction or individual component losses.
- This calculator does not select a pump, determine displacement, calculate flow demand, or verify a motor's electrical rating.
7. Frequently Asked Questions
7.1. What is the difference between hydraulic power and input power?
Hydraulic power is the rate at which the fluid transfers energy. Input power is the estimated power that must be supplied to achieve that hydraulic output after accounting for the entered overall efficiency.
7.2. Why is the input power higher than hydraulic output power?
Because the overall efficiency is below 100%, some input energy is lost through friction, leakage, heat and other effects. The calculator estimates these losses using the efficiency value entered.
7.3. What efficiency value should I use?
Use a value supported by the manufacturer's specifications or a reliable measurement for the equipment and operating condition. A generic assumed efficiency should be treated only as an estimate.
7.4. Does this calculator choose the right pump size?
No. It estimates power only. Pump selection requires additional information such as required flow, pressure, speed, displacement, duty cycle, temperature and manufacturer ratings.
8. Related Hydraulic Calculators
- Hydraulic Cylinder Force Calculator – Push & Pull Force (Tool #001)
- Hydraulic Cylinder Bore Size Calculator (Tool #002)
- Hydraulic Cylinder Flow & Speed Calculator (Tool #003)
- Hydraulic Motor Torque Calculator (Tool #004)
Scope note: This V1 calculator estimates hydraulic output power, required input power and power loss from pressure differential, flow rate and overall efficiency. It does not select or size a pump.
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