Obtain the values to make the calculation. You will need to know the force in pounds (F) and surface area of the piston in square inches (A). If the problem provides "F" in Newtons, you can calculate force in Newtons times 0.225 with the aid of a calculator to obtain force in pounds. If the problem provides "A" in square meters, you can calculate "A" in square meters times 1550 with the aid of a calculator to obtain "A" in square inches.
Simplify the calculation. If you have the "F" and "A" needed to calculate hydraulic system pressure (P) directly, then you can proceed to step 3. If the problem does not provide "F" and "A" needed to calculate "P" directly, you can calculate length in inches times width in inches with the aid of a calculator to obtain "A" in square inches for a rectangular shaped piston or you can calculate pi (3.14) times square radius in square inches with the aid of a calculator to obtain "A" in square inches for a cylindrical shaped piston. You can determine "F" in pounds by calculating work done by a force acting on a piston in pounds feet divided by distance moved by that piston in feet.
Perform the calculation. Calculate "F" divide by "A" with the aid of a calculator to obtain "P" in pounds per square inch.