A pipe specification system which associates certain nominal pipe diameters with standardized wall thickness called “schedules”. The EMT system is identical to the IPS system for all practical purposes. The same schedule number will have a different fixed decimal inch value for each nominal diameter.
For example the wall thickness for 1” Schedule 40 pipe is .133”, but for 2” Schedule 40 pipe is .154”. It is also important to note that the nominal diameter in this system vary considerable from the true diameter. For example, 1” pipe has a true diameter of 1.315” and 2” pipe has a true diameter of 2.375”. Furthermore, the bend radius of pipes in the IPS system are often expressed in terms of “D” of bend. If so, the “D” is the multiple of the pipe’s nominal diameter, not its true diameter. For example, the centerline radius of a 2-“D” bend of a 1” pipe is 2.0” inches, not 2.63” inches.