Oil per stroke for a hydraulic cylinder, with stroke time and return flow.
Adds stroke times and the return flow.
Adds up the volume swing in the tank.
Example Result
Your result will appear here
The calculated result will appear here after you press Calculate.
A hydraulic cylinder takes more oil to extend than to retract, because the rod fills part of the space on the return side. Enter the bore, rod and stroke to get the oil per stroke in each direction. Add the pump flow to see how long each stroke takes and how much oil comes back to tank.
Choose metric or US units.
Enter the bore, the rod diameter and the stroke.
Add the pump flow for stroke times and the return flow.
Add the number of cylinders that move together to see the tank swing.
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Drafted with AI assistance; calculations checked against primary sources and tested with the site's own code. About FlowUtil
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D is the bore and d is the rod. In metric, mm³ ÷ 1,000 gives mL. In US units, in³ ÷ 231 gives gallons.
At 20 L/min from the pump, extending takes 2.513 ÷ 20 × 60 = 7.5 s. Retracting takes 3.8 s. The cylinder comes back twice as fast because the same flow fills a smaller space. Pump flow comes from the hydraulic pump flow calculator.
At 10 gpm, that is 3.7 s out and 2.0 s back.
While a cylinder retracts, the pump fills the small rod side and the large bore side empties. The return flow is the pump flow times the area ratio:
Return flow = Q × D² ÷ (D² − d²)
| Cylinder | Area ratio | Pump flow | Return flow |
|---|---|---|---|
| 80/56 mm | 1.96 | 20 L/min | 39 L/min |
| 3/2 in | 1.80 | 10 gpm | 18 gpm |
Check the return line, valve and filter for the higher flow, not the pump flow. An undersized return path adds back pressure and heat, and that back pressure acts on the cylinder too. The hydraulic pressure calculator shows how much force each side gives.
Oil in the rod side leaves the tank only while the rod is out, so the tank level moves by the rod volume with every full stroke. Two of these 80/56 cylinders moving together swing the level by 2.46 L. That number belongs in the hydraulic reservoir size calculator on top of the normal fill.
The result is the swept volume only. It does not count oil in hoses, pipes and the cylinder's dead space, which you fill once at commissioning. It also ignores oil compressibility and leakage, so real stroke times run slightly long. For a double-rod cylinder, both directions use the annulus area, and for a single-acting cylinder only the extend volume comes from the pump.
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