If you’ve ever stood over a pump spec sheet trying to figure out actual output versus theoretical numbers, you've encountered a familiar challenge. Calculating hydraulic power can be tricky if you don’t start with the right formula. A hydraulics engineer needs a clear method that accounts for pressure, flow and efficiency without switching between units or making incorrect assumptions.
So, let’s take a look at exactly how to calculate hydraulic power properly, using pressure and flow rate as your main inputs.
The basic hydraulic power formula is:
P (kW) = (Q × P) / 600
Where:
This is the theoretical power. It's what you'd get from a system with zero losses. But we all know real systems aren't that efficient, so you’ll need to adjust for that.
A theoretical calculation gives you a ballpark. But once you throw in friction, leakage, temperature, or imperfect pump design, you’ll lose power. That’s where system efficiency comes in.
To calculate actual hydraulic power, you can use this formula:
P_actual (kW) = (Q × P × η) / 600
Where:
Realistically, most hydraulic pumps will sit somewhere between 80% and 90% efficiency, but you need to get that from the actual component data. If you skip this step, you’ll overspec your electric motor or undersize your pipework.
Hydraulic calculations revolve around flow rate and pressure, but they affect different outcomes.
You can have high flow with low pressure (fast but weak), or high pressure with low flow (strong but slow). The ideal setup depends on the application load and how fast you need to cycle the system.
A hydraulic pump doesn’t generate pressure; it creates flow. Pressure is a byproduct of resistance in the system. That’s why when you plug flow and pressure into a formula, you're only halfway there without knowing the pump efficiency.
Pump performance depends on:
Look at the manufacturer’s spec sheet for the pump and motor combination. The closer you match load profile to component efficiency sweet spots, the better your power output.
To save time, use Hydrastore’s Hydraulic Power Calculator. Enter your:
The calculator automatically returns the power output in kW. It’s useful during system design and also when troubleshooting a pump or motor. You can access it directly on our website, no need to convert PSI to bar or gallons to litres.
Keep in mind:
Getting the formula right is just one part. Your hydraulic system design must match the calculated values. That includes:
Choosing a motor too large will leave you with wasted energy. Undersizing leads to overheating or failure. Match components based on power demand and load cycles.
Always use L/min for flow and bar for pressure when using the metric formula. The constant “600” converts units to kilowatts.
No. For imperial, use:
HP = (Q × P × Eff) / 1714
Where Q is in GPM, P is in PSI, and HP is horsepower.
Most run between 0.8 - 0.9. But it depends on the age, design, and condition of the system.
You’ll need to measure it using a flow meter or refer to the pump spec.
Using the right hydraulic power formula helps avoid sizing errors, underperformance or component failure. Whether you’re designing a new system or auditing an existing one, always run both the theoretical and actual numbers. Then match your components to what the job actually needs, don’t guess!
If you're not sure, speak with one of our expert engineers. Hydraulic systems don’t leave much room for error when they’re under load.
Posted by admin in category Hydraulic Systems Advice on Monday, 5th January 2026
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