Keep the units consistent
With displacement V in cm³/rev and speed n in revolutions per minute, theoretical flow Q is V × n ÷ 1,000 in litres per minute. The divisor converts cubic centimetres to litres.
For example, 40 cm³/rev at 1,500 rpm gives 60 L/min theoretical flow. At an assumed volumetric efficiency of 90%, the estimated delivered flow is 54 L/min. That efficiency is an assumption, not a Renowell test result.
Why actual delivery differs
Internal leakage means delivered flow is lower than the ideal calculation. Efficiency depends on the particular pump and operating conditions. Use the relevant performance data to move from an estimate to a selection.
Use calculations as a starting point
The calculator below does not check speed limits, pressure ratings, suction conditions or fluid compatibility. A mathematically valid result can still describe an unsuitable operating point. Confirm the model’s operating envelope before procurement.
ENGINEERING TOOL
Pump flow calculator
Estimate flow from displacement and shaft speed. Enter your own efficiency assumption.
Q theoretical = displacement × speed ÷ 1,000
Q estimated = Q theoretical × efficiency ÷ 100
The default 90% efficiency is an illustrative assumption. This tool does not validate pump ratings, fluid compatibility or suitability for an application.
References & further reading
Bosch Rexroth — Hydraulics: compact knowledge ↗Educational material, not a model-specific operating or repair instruction. Use the applicable equipment and product documentation for the installation.