The psi, or pounds per square inch, is a pressure (P) unit that is measured in feet per second (FPS). Divide the force applied (F) by the area to get psi (A).
Determine the force that has been applied.
Make use of a force gauge, a spring scale, or a strain gauge. Check to see if the unit is in pounds or kilogrammes. If necessary, convert the value.
Calculate the entire area over which force is exerted.
After measuring the length and width and ensuring that the numbers are in the same unit, in this example inches, multiply them.
Calculate the pressure in pounds per square inch (psi).
Divide the calculated force (in pounds) by the calculated area (in square inches).