Pipe schedules

NPS 6 is used as the reference because it is tabulated for essentially every schedule. Mass is for carbon steel at 7,850 kg/m³, so the stainless schedules (5S, 10S, 40S, 80S) would run about 1.9 % heavier in 304 — see the individual schedule pages for material-specific figures.

Open any schedule for its full dimensional table:

• Sch 5S
• Sch 10S
• Sch 10
• Sch 20
• Sch 30
• Sch 40S
• Sch 40 / STD
• Sch 60
• Sch 80S
• Sch 80 / XS
• Sch 100
• Sch 120
• Sch 140
• Sch 160
• XXS
• STD (Standard)
• XS (Extra Strong)

Which schedule is which

Sch 5S

The thinnest stainless schedule. Chosen for low-pressure, high-purity service where wall thickness is set by handling and welding practice rather than by pressure. (25 sizes)

Sch 10S

Common stainless process-piping wall for low-pressure utility and clean service; the stainless counterpart of Sch 10. (25 sizes)

Sch 10

A thin carbon-steel wall used for low-pressure water, slurry and ventilation lines. Rarely specified above NPS 24. (30 sizes)

Sch 20

An intermediate wall sitting between Sch 10 and Sch 40. It appears mainly on larger sizes where Sch 10 is too thin and Sch 40 is over-specified. (15 sizes)

Sch 30

A mid-range wall used where Sch 40 would be heavier than the pressure calculation requires but a standard schedule is still preferred over a non-standard wall. (27 sizes)

Sch 40S

The stainless equivalent of Schedule 40 for sizes up to NPS 8. Above NPS 10, 40S holds a 0.375 in wall while carbon Sch 40 keeps growing. (31 sizes)

Sch 40 / STD

The default carbon-steel wall — Schedule 40 and Standard (STD) are the same thickness below NPS 12. Most general-purpose pipe in the world is Sch 40. (27 sizes)

Sch 60

A non-preferred intermediate wall. It exists mainly so that a mid-pressure line can be specified without moving to a heavier XS wall. (9 sizes)

Sch 80S

Stainless Schedule 80 — the standard stainless wall for higher pressure. Above NPS 10 it holds 0.500 in while carbon Sch 80 continues to grow. (25 sizes)

Sch 80 / XS

Schedule 80 is Extra Strong (XS) below NPS 10. Above that, XS stays at 0.500 in and Sch 80 becomes progressively heavier. (25 sizes)

Sch 100

A non-preferred heavy wall used in high-pressure utility and process service where the next standard step would be too coarse. (9 sizes)

Sch 120

A heavy wall for higher-pressure process lines and steam service. Weight per metre rises sharply, so supports and hangers must be checked with it. (14 sizes)

Sch 140

A very heavy wall used in high-pressure process and power piping; it is where pipe stops competing with fabricated heavy-wall alternatives on cost. (9 sizes)

Sch 160

One of the heaviest tabulated walls, for high-pressure small-bore lines. A Sch 160 line weighs several times its Sch 40 equivalent and needs matching supports. (20 sizes)

XXS

Double Extra Strong — a wall thickness, not a schedule. It is defined independently of Sch 160 and on some sizes is thinner and on others thicker, which is a common source of ordering errors. (14 sizes)

STD (Standard)

Standard wall. Identical to Schedule 40 up to and including NPS 10; from NPS 12 upward it is fixed at 0.375 in and is therefore lighter than Sch 40. (31 sizes)

XS (Extra Strong)

Extra Strong wall. Identical to Schedule 80 up to NPS 8; from NPS 10 upward it is fixed at 0.500 in and is therefore lighter than Sch 80. (31 sizes)

Reading a schedule list correctly

• A schedule number is not monotonic with weight. Sch 40 is heavier than Sch 30 but Sch 60 is not heavier than XXS — the numbered series and the named ones (STD, XS, XXS) come from two different historical systems, and they intersect.
• The stainless schedules are a separate standard. Sch 5S, 10S, 40S and 80S come from ASME B36.19M and are only tabulated to NPS 12 (for 5S and 10S) or with a fixed wall above NPS 10 (for 40S and 80S). Substituting a carbon-steel schedule for a stainless one at a large size is where the two tables disagree most.
• Not every schedule exists at every size. The size count column above varies from 9 to 31. A schedule that is perfectly standard at NPS 6 may simply not be made at NPS 1/2.