The psi, or pounds per square inch, is a unit of pressure (P) using the foot-pound-second (FPS) system. To calculate psi, divide the force applied (F) with the area (A).
- Measure the force applied
Use an instrument such as a force gauge, spring scale or strain gauge. Make sure that the unit is in pounds. Convert the value if necessary.
- Measure the total area on which force is applied
Measure the length and the width, and make sure that both values use the same unit, in this case inches, you can proceed to multiply them.
- Calculate the pressure in psi
Divide the measured force (in pounds) with the measure area (in square inches).