Fluid Power Calculators

Fluid power calculators turn pressure and geometry into actuator force, or turn flow and pressure into pump power and displacement. Cylinder tools use F = P × A. Pump tools use P_hyd = Q·p/600 and Q = V·n·η_vol/1000 for positive-displacement oil pumps.

Three tools cover the usual questions on TaskJunction. Pneumatic Cylinder Force targets shop air. Hydraulic Cylinder Force targets oil-hydraulic pressures at a known bore. Hydraulic Pump Selector sizes drive power, output flow, or required pump displacement.

Single-rod cylinders pull harder on extend than retract. That matters on clamps where retract must clear the part and extend must hold against load. Pump sizing is a separate first pass before you size valves and lines.

Fixture design often starts with a force target: hold this part against a 2 kN milling load at 6 bar shop air. Catalog pages list bores, but you need to know if 40 mm is enough before you burn a mounting plate.

On the power unit side, weak motion might be low pressure, an undersized pump, or a motor that cannot drive the required shaft power. A Q·p power check separates pump limit from valve or flow problem.

Intensifiers downstream of the pump can exceed nominal system pressure at the work port for short strokes. Enter the pressure the piston sees during the hold portion of the cycle, not the standby gauge reading.

• Extend versus retract on the same bore and rod
• Whether available pressure meets a clamp or lift target
• Pump drive power from circuit flow and pressure
• Displacement needed for a target L/min at a known RPM

For cylinders, enter gauge pressure and diameters. Extend uses π/4 × bore². Retract uses π/4 × (bore² − rod²). For pumps, enter flow and pressure for shaft power, or displacement and RPM for output flow. Symbol layout on schematics follows ISO 1219 conventions common in fluid power documentation.

Shop air at 6 bar is not 6 bar at the cylinder after a long line and a undersized FRL. Measure at the port when results disagree with floor observation. Rod buckling and side load on long strokes are outside these forms but often show up when retract force looked fine on paper.

Sequencing matters on real machines. A clamp may need full extend force before the tool engages, while retract only needs enough stroke to clear the part. Pump flow must support the fastest simultaneous actuators on the circuit.

Mobile equipment adds inlet conditions and viscosity limits that static force does not address. Still, if shaft power at working pressure cannot drive the required flow, no valve tuning fixes the pump size.

• Pneumatic tool for air, typically lower pressure and smaller bores
• Hydraulic force tool for industrial oil pressures at known geometry
• Pump selector when you need power, flow, or displacement
• Run extend and retract on one form before fixing rod diameter

Open these during fixture layout, HPU concept, actuator troubleshooting, or homework. You need either known geometry and pressure for cylinders, or flow/pressure/RPM for pumps.

Rodless cylinders and cable cylinders spread force across a different area definition. Map catalog effective area into the bore field or use a dedicated vendor worksheet when geometry is nonstandard.

Intensifiers and pressure boosters change available pressure at the work port. Enter the pressure the piston actually sees, not the pump standpipe gauge, when those devices sit in the line.

Centrifugal water pumps with head and NPSH belong on the pump power / thermal-fluids side of the site, not the oil PD pump selector.

Beam supports and motor torque for the same frame belong in Mechanical Calculators. Feeds for the part in the fixture are under Machining & CNC on the site.

• Clamp and press fixture sizing
• Hydraulic power unit motor and pump screening
• Class problems on cylinder areas and pump displacement
• Not for certified lifting without full standards review
• Regenerative extend circuits need manual area adjustment to match real plumbing

Shop air at 6 bar is not 6 bar at the cylinder after a long line and undersized FRL. Measure at the port when results disagree with floor observation. For pumps, use the flow the circuit actually needs at working pressure, not nameplate relief setting alone.

• Gauge pressure at the port, not absolute unless the form says so
• Bore and rod diameter from catalog or caliper (cylinder tools)
• Circuit flow, pressure, and drive RPM (pump selector)
• One unit system end to end on the form
• Efficiency guidance when you do not have a measured curve

Shop air and known bore: Pneumatic Cylinder Force Calculator. Hydraulic system with known geometry: Hydraulic Cylinder Force Calculator. Oil pump power, flow, or displacement: Hydraulic Pump Selector Calculator. Centrifugal head/flow power: Pump Power Calculator under Thermal & Fluids.