Enter the pump flow, the cylinder size and the stroke. The calculator gives speed and stroke time in both directions.
Extending speed
mm/s
Retracting speed
mm/s
Time to extend
s
Time to retract
s
How cylinder speed is calculated
A cylinder moves as fast as the oil flow can fill it. The speed is the flow divided by the area the oil acts on:
vextend = Q ÷ (π ÷ 4 · D²)
vretract = Q ÷ (π ÷ 4 · (D² − d²))
t = stroke ÷ v
With Q in m³/s (l/min ÷ 60,000) and diameters in metres.
Worked example
A 63/36 mm cylinder receives 20 l/min. It extends at 107 mm/s and retracts at 159 mm/s. A 500 mm stroke takes 4.7 s out and 3.1 s back.
Flow needed for a target speed
Bore (mm)
Flow for 0.1 m/s extending (l/min)
40
7.5
50
11.8
63
18.7
80
30.2
100
47.1
125
73.6
Practical points
Only the flow that actually reaches the cylinder counts. Relief valves, flow controls and leaks in the pump reduce it under load.
Regenerative circuits route the rod-side oil back to the piston side and make extension much faster, at the cost of force.
Above about 0.5 m/s, end cushioning and suitable seals become important.
Questions and answers
How do I calculate hydraulic cylinder speed?
Speed = flow ÷ area. Convert l/min to m³/s by dividing by 60,000 and divide by the piston area in m². For retracting, use the annulus area (piston minus rod).
Why does the cylinder retract faster?
The same oil flow fills a smaller volume on the rod side, because the rod takes up space. The cylinder therefore retracts faster but with less force.
How do I calculate the flow I need for a given speed?
Flow (l/min) = speed (m/s) × piston area (m²) × 60,000. A 63 mm bore extending at 0.1 m/s needs about 18.7 l/min.