The schedule number on pipe products relates to the thickness of the wall on the pipe: as the number increases, the thicker the wall thickness becomes. Also, while the schedule number can be the same on different sized pipes, the actual wall thickness will be different. Here are a few examples:
Pipe size 1.000” Schedule 40 – The actual wall thickness is 0.133”
Pipe size 2.000” Schedule 40 – The actual wall thickness is 0.154”
Pipe size 1.000” Schedule 80 – The actual wall thickness is 0.179”
Pipe size 2.000” Schedule 80 – The actual wall thickness is 0.218”
What we can see here is that the schedule number increases the wall size, and that the wall thickness changes based on the nominal pipe size (NPS).
The best way to see the relationship between pipe size, schedules and wall thicknesses is simply to refer to a conversion chart (below):
There are several schedule numbers used on pipe, such as schedules: 5, 5S, 10, 20, 30, 40, 60, 80, 100, 120, 140, 160, STD, XS and XXS. The most common ones used are schedules 40 and 80