Stainless Pipe Schedules
What the S in 10S actually means, wall thickness for every B36.19M size, and the two places where an S-schedule stops matching the carbon steel schedule of the same number.
- Standard
- ASME B36.19M
- Schedules
- 5S, 10S, 40S and 80S
- 40S and 80S published to
- NPS 12
- 5S and 10S published to
- NPS 30
The S means stainless, not thinner
The most common belief about the S-schedules — that they are a thin-wall series with no carbon steel equivalent — is wrong. In most sizes an S-schedule carries exactly the same wall as the B36.10M schedule of the same number. What the S actually designates is the standard the pipe is made to: ASME B36.19M, the stainless steel pipe standard, with its own material scope, its own tolerances and a shorter size range.
Where the two standards actually disagree
Computed from the two tables rather than asserted — these are the only wall thickness disagreements between the S-schedules and their B36.10M counterparts:
| Stainless | Carbon steel counterpart | Verdict | Detail |
|---|---|---|---|
| Sch 5S | Schedule 5 | Matches Schedule 5 | identical wall in all 21 sizes |
| Sch 10S | Schedule 10 | Matches Schedule 10 | identical wall in all 24 sizes |
| Sch 40S | Schedule 40 | Differs at NPS 12 | 0.375 in against Schedule 40's 0.406 in |
| Sch 80S | Schedule 80 | Differs at NPS 10 and NPS 12 | 0.500 in against Schedule 80's 0.594 in and 0.500 in against Schedule 80's 0.688 in |
Where a schedule “matches”, it matches only across the sizes B36.19M publishes — which is a far shorter list than B36.10M's.
The size range is the bigger difference
B36.19M publishes 40S and 80S only through NPS 12, and 5S and 10S only through NPS 30. B36.10M runs to NPS 36 and beyond in the numbered schedules. A drawing calling for “NPS 16, 40S” is asking for something the standard does not define — the intention is almost always NPS 16 Schedule 40 in a stainless grade, ordered to B36.10M dimensions.
Stainless S-schedule dimensions
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Size | OD | Sch 5S | Sch 10S | Sch 40S | Sch 80S |
|---|---|---|---|---|---|
| NPS 1/8 | 0.40510.29 mm | — | 0.0491.24 mm | 0.0681.73 mm | 0.0952.41 mm |
| NPS 1/4 | 0.54013.72 mm | — | 0.0651.65 mm | 0.0882.24 mm | 0.1193.02 mm |
| NPS 3/8 | 0.67517.14 mm | — | 0.0651.65 mm | 0.0912.31 mm | 0.1263.20 mm |
| NPS 1/2 | 0.84021.34 mm | 0.0651.65 mm | 0.0832.11 mm | 0.1092.77 mm | 0.1473.73 mm |
| NPS 3/4 | 1.05026.67 mm | 0.0651.65 mm | 0.0832.11 mm | 0.1132.87 mm | 0.1543.91 mm |
| NPS 1 | 1.31533.40 mm | 0.0651.65 mm | 0.1092.77 mm | 0.1333.38 mm | 0.1794.55 mm |
| NPS 1 1/4 | 1.66042.16 mm | 0.0651.65 mm | 0.1092.77 mm | 0.1403.56 mm | 0.1914.85 mm |
| NPS 1 1/2 | 1.90048.26 mm | 0.0651.65 mm | 0.1092.77 mm | 0.1453.68 mm | 0.2005.08 mm |
| NPS 2 | 2.37560.32 mm | 0.0651.65 mm | 0.1092.77 mm | 0.1543.91 mm | 0.2185.54 mm |
| NPS 2 1/2 | 2.87573.02 mm | 0.0832.11 mm | 0.1203.05 mm | 0.2035.16 mm | 0.2767.01 mm |
| NPS 3 | 3.50088.90 mm | 0.0832.11 mm | 0.1203.05 mm | 0.2165.49 mm | 0.3007.62 mm |
| NPS 3 1/2 | 4.000101.60 mm | 0.0832.11 mm | 0.1203.05 mm | 0.2265.74 mm | 0.3188.08 mm |
| NPS 4 | 4.500114.30 mm | 0.0832.11 mm | 0.1203.05 mm | 0.2376.02 mm | 0.3378.56 mm |
| NPS 5 | 5.563141.30 mm | 0.1092.77 mm | 0.1343.40 mm | 0.2586.55 mm | 0.3759.52 mm |
| NPS 6 | 6.625168.27 mm | 0.1092.77 mm | 0.1343.40 mm | 0.2807.11 mm | 0.43210.97 mm |
| NPS 8 | 8.625219.07 mm | 0.1092.77 mm | 0.1483.76 mm | 0.3228.18 mm | 0.50012.70 mm |
| NPS 10 | 10.750273.05 mm | 0.1343.40 mm | 0.1654.19 mm | 0.3659.27 mm | 0.50012.70 mm |
| NPS 12 | 12.750323.85 mm | 0.1563.96 mm | 0.1804.57 mm | 0.3759.52 mm | 0.50012.70 mm |
| NPS 14 | 14.000355.60 mm | 0.1563.96 mm | 0.1884.78 mm | — | — |
| NPS 16 | 16.000406.40 mm | 0.1654.19 mm | 0.1884.78 mm | — | — |
| NPS 18 | 18.000457.20 mm | 0.1654.19 mm | 0.1884.78 mm | — | — |
| NPS 20 | 20.000508.00 mm | 0.1884.78 mm | 0.2185.54 mm | — | — |
| NPS 24 | 24.000609.60 mm | 0.2185.54 mm | 0.2506.35 mm | — | — |
| NPS 30 | 30.000762.00 mm | 0.2506.35 mm | 0.3127.92 mm | — | — |
Each schedule in full
Common questions
Is 10S the same as Schedule 10?
In wall thickness, yes, in every size B36.19M publishes. The difference is the standard: 10S is stainless pipe to ASME B36.19M, which stops at NPS 30, while Schedule 10 is B36.10M and continues further.
Is 40S the same as Schedule 40?
Up to NPS 10, yes. At NPS 12 they part company — 40S is 0.375 in while Schedule 40 is 0.406 in — and B36.19M does not publish 40S above NPS 12 at all.
Is 80S the same as Schedule 80?
Up to NPS 8, yes. At NPS 10 and NPS 12, 80S holds at 0.500 in while Schedule 80 climbs to 0.594 in and 0.688 in. Above NPS 12 there is no 80S.
Can I order stainless pipe in a plain numbered schedule?
Yes, and above the S-schedule size limits you have to. Stainless pipe to ASTM A312 is routinely supplied to B36.10M schedules; the S designation is a convenience for the thin end of the range, not a requirement for stainless.