You are holding an old pump pulled from a machine. The sticker has long worn off, and the only thing you could decipher from the old engravings is a mysterious "14 cc" or "16 cm³/rev."
For a hydraulic engineer, this is the most important information, but for a service technician building a system, the problem remains: how many liters per minute is that exactly? After all, that determines how fast the cylinder will operate and how thick the hoses need to be.
With our free tool from BRhydraulic, you can convert the pump's displacement into actual system output in a fraction of a second!
Hydraulic Pump Flow Calculator
Calculate actual oil flow (L/min) based on displacement.
What is pump displacement (working volume)?
The parameter given in cm³/rev (or "cc" for cubic centimeters) simply determines how much oil the pump can displace during one full rotation of the shaft.
However, this does not give us direct information about the efficiency of the entire system until we know what is driving the pump. A different flow will be obtained by connecting the same pump to a tractor's PTO shaft (540 rpm), and a completely different one by coupling it with a high-speed internal combustion engine (3000 rpm).
Our calculator takes into account the most popular drive types to instantly calculate your result.
Why is actual flow lower than theoretical flow?
In the calculator, you will find a field specifying the pump's condition, known in engineering as volumetric efficiency. Hydraulic pumps are never 100% sealed internally. There is always a microscopic gap between the gears and the pump body, through which oil (especially under high pressure) "flows back," not reaching the system.
- A new, high-quality gear pump delivers about 95-96% of the theoretical volume.
- A worn pump that has been operating for years with contaminated oil may have an efficiency of around 85% or less (this is why machines become slow over time!).
How to calculate this on paper? (Formulas)
The formula for converting displacement to flow in liters is very simple:
Formula for actual flow:
Q = (V * n * eff) / 1000
Where:
Q– actual pump flow in liters per minute (L/min)V– displacement / working volume in cm³/revn– engine speed in revolutions per minute (RPM)eff– volumetric efficiency (e.g., 0.95 for 95%)1000– conversion factor from cubic centimeters to liters
Find a new pump at BRhydraulic
Has your pump lost efficiency and your machine is running in slow motion? Or are you designing a new system and looking for top-quality components?
- Solenoid valves: Ensure precise control of oil direction and flow in your system.
- Cylinders: A wide selection of ready-to-use cylinders with various strokes and diameters, ready for operation in the harshest conditions.
- CETOP manifolds: Modular connection plates and manifolds facilitating the construction of compact and efficient hydraulic systems.
