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.