Pipe Schedule Chart (SCH 5 to XXS, NPS 1/8" to 48") with Wall Thickness and Weight

The full chart follows the summary. Search by NPS or DN, highlight a schedule, and switch between metric and imperial units. Need it on paper? Get the printable PDF from the WhatsApp button further down.

TL;DR

• Pipe schedule is a wall-thickness designation; the higher the number, the thicker the wall.
• OD is fixed for each NPS, so a thicker wall reduces the inside diameter.
• From NPS 14 upward, the OD in inches equals the NPS: NPS 14 is 14.000 in (355.6 mm).
• SCH 40 equals STD up to NPS 10; from NPS 12 STD stays at 9.53 mm while SCH 40 keeps growing.
• SCH 80 equals XS up to NPS 8; from NPS 10 XS stays at 12.70 mm.
• Carbon steel schedules come from ASME B36.10M; stainless 5S, 10S, 40S and 80S come from ASME B36.19M.
• The schedule is chosen from a wall thickness calculation, then fixed for each size in the project's line class.

Pipe Schedule Chart: OD, Wall Thickness and Weight

Each cell: wall thickness (top) and weight per unit length (bottom, plain-end carbon steel). "-" means the standard lists no wall for that size and schedule. Carbon and alloy steel per ASME B36.10M. Scroll sideways on mobile; the NPS column stays fixed.

Weight is calculated as W (kg/m) = 0.02466 × (OD − t) × t, with OD and t in mm, for carbon steel at 7.85 g/cm³ (Project Materials). For NPS 38 to 48 the chart shows STD and XS only; check ASME B36.10M for other wall thicknesses at these sizes.

Stainless Steel Schedules (ASME B36.19M): 5S, 10S, 40S, 80S

Stainless pipe uses the same ODs but its own "S" schedules under ASME B36.19M, which covers NPS 1/8 to 30 (Project Materials). Do not read a stainless line from the carbon steel columns: from NPS 10 and up, several S walls are thinner than the plain schedule with the same number.

Wall thickness in mm (switches with the units button). Values checked against Engineering ToolBox (NPS 1/8 to 12) and Project Materials (NPS 14 to 30).

What Does Pipe Schedule Mean?

A pipe schedule is a number that designates wall thickness for a given nominal pipe size. For the same NPS, SCH 80 is thicker than SCH 40, and SCH 160 thicker still. The schedule is not a thickness in itself: SCH 40 is 3.38 mm at NPS 1 but 6.02 mm at NPS 4.

The key rule is that the outside diameter stays the same for every schedule of one NPS, so fittings, flanges and supports fit all of them. The wall grows inward. For NPS 1/8 to 12 the NPS is only a nominal label (NPS 4 is 4.500 in OD). From NPS 14 upward, the OD in inches equals the NPS, as the chart shows: NPS 14 = 14.000 in, NPS 24 = 24.000 in (610 mm).

NPS, NB and DN: Pipe Size Naming

NPS (nominal pipe size) is the inch designation used by ASME. DN (diamètre nominal) is the metric equivalent. NB (nominal bore) is the term used on many Indian drawings and in IS 1239, and is written in mm like DN. Indian and Gulf drawings often mix all three, so it pays to know the pairs. Up to NPS 3 the mapping has to be learned; from NPS 4 up, DN = 25 × NPS (Octal Steel).

Schedule 40 vs Schedule 80 vs STD and XS

STD (standard), XS (extra strong) and XXS (double extra strong) are the older weight classes. The numbered schedules came later. They overlap for small sizes and then split, which is a common source of mistakes on bills of material.

How to Choose the Right Pipe Schedule

The schedule is the last step of a pressure design calculation, not a guess. For process piping to ASME B31.3, the minimum thickness follows paragraph 304.1.2 (Project Materials):

1. Design pressure and temperature from the process data or line list.
2. Allowable stress for the pipe material at design temperature, from the code tables.
3. Add the corrosion allowance set by the piping material specification.
4. Allow for mill tolerance: ASTM A106 and A53 permit the wall to be 12.5% under nominal, so divide by 0.875.
5. Round up to the next schedule in the chart. Example: NPS 6 needing 5.23 mm after tolerance gets SCH 40 (7.11 mm).

The full worked calculation is on our pipe wall thickness calculation page.

Pipe Schedules on Indian and Gulf Projects

On both, the piping line class (piping material specification) fixes the schedule for every size in that class, so designers read it from the spec rather than choosing per line. As an illustration, a class might call for SCH 160 on small-bore sizes, SCH 80 on mid sizes and SCH 40 above; the actual split depends on pressure, temperature, material and corrosion allowance.

Frequently Asked Questions

Sources

• ASME B36.10M, Welded and Seamless Wrought Steel Pipe, and ASME B36.19M, Stainless Steel Pipe. Check the current edition before procurement use.
• fluids open-source engineering library (Caleb Bell), piping module: ASME B36.10M schedule data, pypi.org/project/fluids.
• Project Materials: ASME pipe wall thickness charts; Pipe schedule to wall thickness; What is ASME B36.19; Pipe weight; Pipe wall thickness; Small bore piping.
• Engineering ToolBox, "Stainless Steel Pipes: Dimensions and Weights", engineeringtoolbox.com.
• Octal Steel, "Steel Pipe Dimensions and Sizes" (NPS to DN), octalsteel.com.
• Bureau of Indian Standards, IS 1239 (Part 1):2004 product manual, bis.gov.in.

This article was last reviewed on 4 November 2026.