Hydraulic Pump Selector Calculator

Formula

• Hydraulic power: P_hyd (kW) = Q (L/min) × p (bar) / 600.
• Shaft / motor power: P_shaft = P_hyd / η (overall efficiency as a fraction).
• Imperial HP: HP = PSI × GPM / (1714 × η).
• Output flow: Q (L/min) = V (cc/rev) × n (rpm) × η_vol / 1000 · GPM = n × V_in³ / 231.
• Required displacement: V (cc/rev) = Q × 1000 / (n × η_vol) · V_in³ = 231 × GPM / n.
• Drive torque: T (N·m) = 9550 × P_shaft / n.

How it works

Three solve modes for oil-hydraulic pumps. Drive power from flow and pressure (P = Q·p/600, shaft = hydraulic/η). Output flow from displacement and RPM (Q = V·n·η_vol/1000). Required displacement from target flow and RPM. Screening only — not a centrifugal head/NPSH or OEM SKU picker.

Pick Input mode: Drive power (default), Output flow, or Required displacement. Set overall η (shaft power) and η_vol (flow/displacement). On Output flow, pressure is optional — add it to also get shaft power and torque. CALCULATE fills Results and updates the motor→pump sketch. Editing clears Results. RESET restores the 40 L/min · 140 bar defaults.

Drive power from flow and pressure

Default CALCULATE path: P_hyd ≈ 9.33 kW; P_shaft ≈ 10.98 kW at η 85%.

Torque uses T = 9550 × P_shaft / n at the entered pump speed.

Flow from displacement, or displacement from flow

28 cc/rev at 1450 rpm and η_vol 95% → Q ≈ 38.57 L/min.

Target 40 L/min at the same speed → V ≈ 29.04 cc/rev.

What this pad is not

This pad: oil PD pump · Q, p, V, n, η.

Not this pad: system curves, NPSH available, catalog SKU pick.

Worked example

Default Drive power path: 40 L/min, 140 bar, η 85%, 1450 rpm. Reproduce on CALCULATE.

1. Leave Input mode on Drive power · flow + pressure. Confirm η Typical gear/vane 85% and 1450 rpm.
2. P_hyd = 40 × 140 / 600 = 9.333 kW.
3. P_shaft = 9.333 / 0.85 ≈ 10.98 kW ≈ 14.72 HP.
4. T = 9550 × 10.98 / 1450 ≈ 72.3 N·m.
5. Implied displacement at η_vol 95%: V = 40 × 1000 / (1450 × 0.95) ≈ 29.04 cc/rev.

Result: Default: ≈ 10.98 kW shaft (14.72 HP), ≈ 72.3 N·m, ≈ 29.04 cc/rev screening displacement.

When to use

• First-pass motor kW/HP for a hydraulic pump from circuit flow and pressure
• Estimating L/min or GPM from catalog cc/rev and drive RPM
• Sizing required displacement for a target flow at a known speed
• Cross-checking common hydraulic pump toolbox results
• Converting between metric and imperial power formulas

Limitations

• Positive-displacement oil-pump screening — not centrifugal head, NPSH, or system-curve selection.
• Does not pick OEM pump SKUs, mounting, or noise class.
• Overall η and η_vol are presets/guidance, not a measured pump curve.
• Inlet conditions, cavitation, viscosity derating, and thermal duty are out of scope.
• Cylinder bore-from-force sizing is not on this pad — use hydraulic cylinder force with known geometry.
• Manufacturer catalog pickers and full circuit network models stay with the OEM or dedicated hydraulic software.

FAQ

How is this different from the pump power calculator?

Pump power uses ρ·g·Q·H for centrifugal/head applications. This pad uses Q·p/600 for oil-hydraulic positive-displacement pumps and also solves displacement ↔ flow.

What efficiency should I use?

Overall η ~85% is a typical gear/vane first pass; piston pumps often 90%+. Volumetric η_vol ~95% for sizing displacement; use 100% only for theoretical checks. Follow the pump maker when you have a curve.

Why 600 and 1714?

600 converts L/min and bar to kW (from N·m/s). 1714 converts PSI and US GPM to mechanical HP. Same physics with different unit constants.

Can this replace a full hydraulic pump selection tool?

You get the same core PD-pump relations (power, flow, displacement, torque). You do not get product catalogs or every unit toggle — confirm ratings in the manufacturer data.

Does this size a hydraulic cylinder bore?

No. Bore-from-force belongs with cylinder force tools. This pad sizes the pump that supplies the circuit.

What about NPSH and pipe losses?

Out of scope here. Use a centrifugal or system-curve tool when head and suction conditions dominate.