Gulf Coast Air & Hydraulics - Hydraulic Formulas

Hydraulic Formulas

We here at Gulf Coast Air & Hydraulics want to offer you the best in products and information. On this page are some useful formulas and general rules for making your hydraulic calculations. Please feel free to bookmark this page and use it for your reference.

Useful Formulas
Fluid Pressure (PSI) = Force ( pounds) / Area ( sq. in.)	PSI = F/A
Cylinder Area (sq. In.) = 3.1416 × Radius (inch)(sq.)	A = Pi × R(sq.)
Cylinder Force (pounds) = Pressure (psi) × Area (sq. in.)	F = P × A
Cylinder Speed (ft./sec.) = (231 × gpm) / (12 × 60 × Area)	v = (0.3208 × gpm) / A
Hydraulic Horsepower = Pressure (psi) × gpm / 1714	HP = (psi × gpm) / 1714
Fluid Motor Torque (in. lbs.) = Pressure (psi) × disp. (cu.in./ rev.) / 6.2822	T = (P ×d) / (2 ×3.1416) d = disp. rev (cu. in. / rev.)
Fluid Motor Speed (rpm) = (231 × gpm) / disp. (cu. in.)	n = (231 × gpm) / d
Fluid Motor Horsepower = Torque (in. lbs.) × rpm / 63025	HP = TN /63025
Pump Output Flow (gpm) = (Speed (rpm) × disp. (cu. in.)) / 231	gpm = (n ×d) / 231
Pump Input Horsepower = gpm × Pressure (psi) / 1714 × eff.	HP = (Q ×P) / 1714 × E

General Rules

Horsepower for driving a pump: For every 1 hp of drive, the equivalent of 1 gpm @ 1500 psi can be produced.

Horsepower for idling a pump: To idle a pump when it is unloaded will require about 5% of it's full rated power

Wattage for heating hydraulic oil: Each watt will raise the temperature of 1 gallon of oil by 1° F. per hour.

Flow velocity in hydraulic lines: Pump suction lines 2 to 4 feet per second, pressure lines up to 500 psi - 10 to 15 ft./sec., pressure lines 500 to 3000 psi - 15 to 20 ft./sec.; all oil lines in air-over-oil systems; 4 ft./sec.