What Do Pipe Schedules Mean?

What are Pipe Schedules? (Video Update)

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).

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

What does Nominal Pipe Size or NPS mean?

The NPS size represents the approximate inside diameter (not outside) of the pipe; if the schedule number on a set size is changed, it does effect the inside diameter (ID) but not the outside diameter (OD). In 1927 the American Standard Association replaced the previously used Iron Pipe Sizing (IPS) with Nominal Pipe Sizing (NPS).  This North American standard is used on pipes for high or low pressures and temperatures.   Example:

NPS                        OD                          Schedule #          Wall Thickness           ID

1.000”                   1.315”                   SCH 40                  0.133”                         1.049” (approx.)

1.000”                   1.315”                   SCH 80                  0.179”                         0.957” (approx.)

All pipes are specified using the NPS and schedule numbers. It is the schedule number that determines the approximate inside diameter.

Video Update

Don’t have time to read the blog?

Check out the video blog below to learn about pipe schedules.