What does schedule pipe mean? schedule 40, schedule 80

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I am studying for the lubrication engineers exam and need to know more about “schedule pipe” what it means and what do they mean by schedule 40 and schedule 80. And, what is the difference between pipes SCH 40 and SCH 40S?


The pipe schedule refers to the pipe wall thickness. The higher the schedule, the thicker is the pipe wall. For example:

2-inch nominal size steel pipe: schedule 40 has a wall thickness of 0.154 inches and schedule 80 has a wall thickness of 0.218 inches.

4-inch nominal size steel pipe: schedule 40 has a wall thickness of 0.237 inches and schedule 80 has a wall thickness of 0.318 inches.

As you can see, the relationship between schedule and wall thickness changes with the
pipe nominal size.

Table 6-6 in Perry’s Chemical Engineers’ Handbook (Sixth Edition) provides the schedule thicknesses for steel pipe nominal sizes ranging from 1/8 of an inch to 30 inches. I am sure similar tabulations are available in other books as well.

The schedules that end in S (5S, 10S, 40S, & 80S) are for stainless steel pipe. In MOST smaller pipe sized (<8") schedule 40 and schedule 40S have the same wall thickness. In larger diameter pipes, they do not. Also, there are no schedule 5 or 10 carbon steel pipes until you get into very large (>14") sizes.

For pipe schedules, see:




Pipe Schedule is the term used to describe the thickness of a pipe. The outside diameter of a pipe is the same for all Schedules in a particular nominal pipe diameter. Standard standard pipe schedules or pipes sizes as given by ANSI / ASME B36.10M and API 5L. There are eleven schedule numbers commonly used: 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, & 160.

Pipe corridorPipe corridorThe most popular schedule, by far, is 40. For pipe 8-inches and under, Schedule 40 and Standard Weight pipe wall thicknesses are the same. Schedules 5, 60, 100, 120, & 140 are rarely used. This should be considered when piping is specified for a particular project.

The schedule number is defined as the approximate value of the expression:

Schedule Number = (1,000)(P/S)


P = the internal working pressure, psig

S = the allowable stress (psi) for the material of construction at the conditions of use.

For example, the schedule number of ordinary steel pipe having an allowable stress of 10,000 psi for use at a working pressure of 350 psig would be:

Schedule Number = (1,000)(350/10,000) = 35 (approx. 40)


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Interesting information, dik.

Stuff I didn’t know until I looked for it…


Length of steel pipe can be somewhat unusual, too. Of course you can get “cut lengths” to your specification. But for if only long, straight pipe (without pipe threads) is needed the order can be placed for “random lengths” (18’ to 25’) or “double random lengths” (38’ to 40’). May be able to order pipe even longer than double random lengths.

I learned this some years ago when designing/constructing a 1000’+ long, straight as an arrow, pipeline from 8" Schedule 40 pipe. Using double random lengths halved the number of welds.

On other sites, I’ve heard that rolled ‘stuff’ can come in 80’ lengths if ordered specially. Likely running into over length highway restrictions.