Hydraulic calculators
Calculators for basic hydraulic sizing. Enter the input values and the results update automatically.
Gear pump or motor measurement
Measure a dismantled pump or motor and estimate its displacement. An indicative result for identification – the true value is confirmed from the name plate or the manufacturer's table.
Pump flow rate
Calculates how much oil the pump delivers. Manufacturers state the displacement (cm³/revev) in the pump's technical data – it is often part of the type designation. Without an efficiency value the result is theoretical.
Pump displacement
The opposite of the pump flow rate calculator: tells what size of pump is needed for the required flow. Compare the result with the displacements stated in manufacturers' technical data and choose the nearest standard size.
Pump power requirement
Calculates how much shaft power is needed to drive the pump at the selected pressure and flow. For electric motor selection there is a separate calculator with a safety factor.
Electric motor selection
Sizing of the power unit's electric motor for continuous duty. In short-term duty (e.g. lifts) the motor can briefly be loaded above its rated power.
Pump efficiency
Compares the hydraulic power delivered by the pump with the power taken from the shaft – a handy condition check. A new pump typically has an overall efficiency of 80–90%; a clearly lower value indicates wear.
Hydraulic motor sizing
Calculates what size of hydraulic motor is needed for the required torque at the available pressure – plus the speed and power at the selected flow. Compare the displacement with the manufacturer's table and choose the nearest standard size.
Hydraulic motor torque
The opposite of the hydraulic motor sizing calculator: tells how much torque a known motor delivers at the available pressure – plus the speed and power at the selected flow. Manufacturers state the displacement in the motor's technical data.
Motor speed
Calculates how fast the motor turns with the flow supplied to it. A larger displacement turns more slowly at the same flow but delivers more torque.
Motor flow requirement
Tells how much flow must be supplied to the motor for it to run at the required speed. Motor leakage increases the demand, which is why the value is divided by the efficiency – unlike in pump output.
Motor pressure
Tells how much pressure is needed for the motor to produce the required torque. If the result exceeds the system pressure level, choose a larger displacement.
Torque from power
Calculates the torque available at the shaft from power and speed – e.g. the shaft torque of an electric motor or engine driving a pump. Power, torque and speed are tied together: knowing two gives the third.
Flow rate from power
Tells how much flow is needed for the required hydraulic power at the selected pressure differential – e.g. a quick estimate of an actuator's flow demand during system design.
Pressure from power and flow
The third form of the same power–pressure–flow relationship: tells what pressure differential corresponds to the required power at the selected flow.
Speed from power and torque
Calculates the speed when power and torque are known – e.g. a check whether the motor's power is sufficient for the required torque at the desired speed.
Force from area
Calculates the force with which pressure acts on a surface: one bar equals 10 N/cm². Cylinder push and pull forces are available directly from the basic cylinder sizing calculator.
Flow velocity in a tube
Checks whether the tube size is sufficient: too high a flow velocity causes pressure losses, noise and heating. Guide values: suction line 0.5–1.5 m/s, return line 2–4 m/s, pressure line 3–6 m/s.
Flow velocity in a hose
The same check for hoses – enter the hose's actual inside diameter. Common hose sizes: 1/4″ = 6.4 mm, 3/8″ = 9.5 mm, 1/2″ = 12.7 mm, 3/4″ = 19 mm, 1″ = 25.4 mm.
Tube pressure rating
Barlow's formula for a straight tube. Indicative – it does not replace dimensioning to standards. Bends and welds weaken the tube.
Typical efficiencies
Use these values in the calculators' efficiency fields when the exact value is not known.
Oil volume changes
Typical values for mineral oil: thermal expansion coefficient β = 0.0007 1/°C and bulk modulus K ≈ 14,000 bar.
Accumulator sizing and pre-charge
Sizing by the gas law
Gas law p · Vⁿ = constant. The calculator converts pressures to absolute (+1 bar). Fill in V0 or ΔV – the other one is calculated.
Pre-charge recommendation
For diaphragm accumulators typically 0.6–0.9 × P1. Always check the manufacturer's instructions.
Charging pressure temperature correction
T in kelvin, pressures absolute. Always charge the accumulator with nitrogen – never with oxygen or compressed air. An accumulator is a pressure vessel: follow the manufacturer's instructions and regulations.
Basic cylinder sizing
Push force is calculated on the full piston area, pull force on the annulus (piston − rod). Theoretical values without friction and back-pressure losses.
Piping sizing and pressure drop
For a straight tube: with laminar flow λ = 64/Re, with turbulent flow by the Blasius formula λ = 0.3164/Re0.25. Bends, fittings and valves add to the losses.
Thermal calculators
Oil heating
Reservoir heat dissipation
Required cooling flow
Typical values used in the calculation: oil volumetric heat capacity approx. 1.66 kJ/(l·°C) and steel reservoir heat transfer coefficient approx. 12 W/(m²·°C) (without a fan). The values are indicative.
Orifice calculators
Flow through an orifice
Equivalent orifice, parallel
Equivalent orifice, series
Calculation for a sharp-edged orifice: discharge coefficient α = 0.7 and oil density 870 kg/m³. The actual flow depends on the orifice shape and the oil viscosity.
Metal weight calculator
A hexagonal bar is measured across flats (A/F), i.e. the distance between opposite faces – the same as the spanner size (e.g. A/F 17 = 17 mm spanner). For tubes, enter the outside dimension and the wall thickness. Theoretical weight without tolerances.
Plate / flat bar
The calculators and tables on this page are indicative aids only. They are based on general theoretical formulas and typical tabulated values, and do not account for all real-system conditions such as losses, temperatures, tolerances, material differences or component condition and wear. The results must not be used as the sole basis for dimensioning, manufacturing or safety; always verify dimensioning and suitability against the component manufacturer's official technical data and the applicable standards and regulations. PV-Hydrauli Oy accepts no liability for possible errors in this information or for any direct or indirect damage arising from its use. If in doubt, we are happy to help – Contact.