Torque and Horsepower relations:
T = HP x 5252 ÷ RPM
HP = T x RPM ÷ 5252
RPM = HP x 5252 ÷ T
Torque values are in foot pounds

Hydraulic (fluid power) horsepower:
HP = PSI x GPM ÷ 1714
PSI is a gauge pressure in pounds per square inch.
GPM is oil flow in gallons per minute.

Velocity of oil flow in a pipe:
V = GPM x 0.3208 ÷ A
V is oil velocity in feet per second. GPM is flow in gallons per minute. A is inside area of pipe in square inches.

Charles' Law for behaviour of gases:
T1V2 = T2V1, or T1P2 = T2P1
T1 ,P1 and V1 are initial temperature, pressure and volume.
T2 ,P2 and V2 are final conditions.

Boyles' Law for behaviour of gases:
P1,V1 = P2,V2
P1 and V1 are initial pressure and volume.
P2 and V2 are final conditions.

Heat Equivalent of Fluid Power:
BTU per hour = PSI x GPM x 1-1/2

Burst pressure of pipe or tubing:
P = 2t x S ÷ 0
P is burst pressure in PSI, t is wall thickness, in inches.
S is tensile strength of material in PSI.
0 is outside diameter, in inches..

Thrust of force of any cylinder:
T = A x PSI
T is thrust of force, in pounds. A is piston net area in square inches. PSI is gauge pressure.

Hydraulic cyl. piston travel speed:
S = CIM ÷ A
S is piston travel speed, inches per minute. CIM is oil flow into cylinder, cubic inches per minute.
A is piston area in square inches.

Pressure loss per foot of pipe:
P = V x Q ÷ 18,300 D4
P is pressure loss in PSI per foot of pipe length.
V is SSU viscosity at operating temperature.
Q is GPM flow. D is inside diameter of pipe in inches.

Force for piercing
of shearing sheet metal:
F = P x T x PSI
F is force required, in pounds.
P is perimeter around area to be sheared, in inches.
T is sheet thickness in inches. PSI is the shear strength rating of the material in pounds per square inch. 

Heat radiating capacity
of a steel reservoir:
HP = 0.001 x A x TD
HP is the power radiating capacity
expressed in horsepower.
A is surface area, in square feet. TD is temperature
difference in 0F between oil andsurrounding.

Effective force of a cylinder working at an angle to direction of the load travel:
F = T x sin A
T is the total cylinder force, in pounds.
F is the part of the force which is effective, in pounds.
A is the least angle, in degrees, between cylinder axis and load direction.