Schedule is a number used to define the thickness of a pipe wall; the thickness determines how much pressure the pipe can withstand. Pipe schedule is the ratio of internal pressure (psi) divided by the allowable stress (psi), multiplied by 1,000. The higher the schedule, the greater the wall thickness and ability to withstand pressure. Common schedules include 10, 40, 80, and 160. Many industries have schedule requirements for specific applications, so it is important to ensure that the pipe’s schedule meets safety and operational standards.