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Free engineering tools
Eleven quick sizing tools our engineers use every day — cylinder force and speed, pump flow, motor kW, tank and hose size, air consumption, compressor size, leak cost and air pipe size. Change any value and the result updates instantly.
Hydraulic
For cylinders, power packs and pipework. Metric inputs; results also shown in tonnes, HP and US units where useful.
Push and pull force from bore, rod and working pressure.
FormulaF = p × A × η. A = πD²/4 (push), π(D² − d²)/4 (pull). 1 bar = 0.1 N/mm².
Result
How fast a cylinder moves on a given pump flow — or the flow you need for a target speed.
Formulav = Q / A. Q in L/min × 10⁶ ÷ 60 = mm³/s. Retract is faster because the annulus is smaller.
Result
Delivery of a gear, vane or piston pump at a given speed.
FormulaQ (L/min) = cc/rev × rpm × ηv ÷ 1000. Use 1440 rpm for a 4-pole motor on 50 Hz, 2880 for 2-pole.
Electric motor needed to drive the pump at your flow and pressure.
FormulaMotor kW = p (bar) × Q (L/min) ÷ (600 × η). Size the motor for the highest pressure-and-flow point of the cycle.
Result
Rule-of-thumb oil reservoir for an industrial power pack.
FormulaOil volume = k × Q. Use 3× with an oil cooler, 4× for general duty, 5× for continuous or hot-running duty. Gross adds ~15% air space.
Result
Minimum inside diameter to keep oil velocity in the recommended range.
Formulad = √(4Q ÷ πv). Typical velocities: suction 0.6–1.2 m/s, return 2–4 m/s, pressure 3–6 m/s.
Result
Pneumatic
For air cylinders, compressors and distribution. Pressures are gauge (bar g); air volumes are free air at 1.013 bar and 20 °C.
Force from an air cylinder at your supply pressure, with a safe working-load figure.
FormulaF = p × A × η. For moving loads, size the cylinder so the load is no more than 70% of this force (50% for fast or cushioned work).
Result
Free air a cylinder uses, in normal litres per minute — the number compressor sizing starts from.
FormulaFree air = (A_extend + A_retract) × stroke × (p + 1.013) ÷ 1.013 × cycles × cylinders. Add 10–15% for tubing and valve dead volume.
Result
Free air delivery (FAD) and approximate compressor motor size for the whole plant.
FormulaFAD = demand × (1 + leakage) × (1 + expansion). Specific power ≈ 6–7 kW per m³/min for an oil-injected screw compressor at 7 bar.
Result
What a leak costs in electricity over a year — most plants have dozens.
FormulaChoked flow through a sharp-edged hole, discharge coefficient 0.65, air at 20 °C. Energy = air lost × specific power × hours.
Result
Main-line bore that keeps the pressure drop within your limit.
FormulaΔp = 450 × q¹·⁸⁵ × L ÷ (d⁵ × p), with q in L/s free air, d in mm, p in bar absolute. Add 30–50% to pipe length for bends, tees and valves.
Result
How the maths works
Multiply the working pressure by the area it acts on. On the push stroke the area is the full piston, πD²/4; on the pull stroke it is the annulus, π(D² − d²)/4, where d is the rod. Pressure in bar × 0.1 gives N/mm², so an 80 mm bore at 160 bar pushes about 80 kN, or roughly 8 tonnes, before friction losses.
Flow equals speed × area. For an 80 mm bore extending at 100 mm/s you need about 30 L/min. The retract stroke moves faster on the same flow because the annulus area is smaller than the piston area.
Motor kW = pressure (bar) × flow (L/min) ÷ 600, then divide by the overall pump efficiency — around 0.85 for a gear pump in good condition. 20 L/min at 160 bar needs about 6.3 kW, so a 7.5 kW (10 HP) motor. Size for the highest pressure-and-flow point in the cycle, not the average.
A common rule is three to five times the pump flow per minute: three times when an oil cooler is fitted, four for general industrial duty and five for continuous or hot-running work. Leave roughly 15% of the tank as air space above the oil.
Work out the swept volume on each stroke, multiply by the compression ratio (gauge pressure + 1.013) ÷ 1.013 to convert it to free air, then multiply by cycles per minute and the number of cylinders. A 63 mm double-acting cylinder with a 200 mm stroke at 6 bar and 10 cycles a minute uses about 82 normal litres per minute.
A single 3 mm leak at 6 bar loses about 0.38 m³ of free air a minute, which takes roughly 2.5 kW of compressor power. Over 6,000 running hours at ₹9 per kWh that is around ₹1.3 lakh a year — for one hole. Leak surveys usually pay for themselves within weeks.
These results are estimates for preliminary sizing. Real systems have losses, peaks and safety factors these formulas do not capture — we check every design before it is built.
Send us your figures and the job the machine has to do. We will come back with a circuit, a part list and a price.
