PipeData

Schedule 20 Pipe Dimensions

Wall thickness, bore and plain-end weight for all 15 sizes ASME B36.10M publishes in schedule 20, NPS 8 through NPS 36.

Schedule
Schedule 20
Sizes published
15 (NPS 8 to NPS 36)
Thinnest wall
0.250 in (6.3 mm) at NPS 8
Thickest wall
0.500 in (12.7 mm) at NPS 26
Standard
ASME B36.10M

Where schedule 20 is used

Schedule 20 exists only in the larger sizes. It is a light wall for low-pressure, large-diameter duty such as cooling water, drainage and low-pressure gas.

Pipe wall thickness to scale, Schedule 20Pipe cross-sections drawn to scale at the same outside diameter so the wall thicknesses can be compared. NPS 8: 0.250 in wall on 8.625 in OD; NPS 22: 0.375 in wall on 22.000 in OD; NPS 36: 0.500 in wall on 36.000 in ODNPS 80.250 in wall on 8.625 in ODNPS 220.375 in wall on 22.000 in ODNPS 360.500 in wall on 36.000 in OD
Schedule 20 in three sizes, each drawn to its own scale. The sections are drawn at the same width so that the wall can be compared with the diameter it belongs to. The wall gets thicker as the size goes up, but it takes up a smaller share of the pipe.

Schedule 20 in every size

Dimensions are given in inches, with the millimetre equivalent beneath in grey.

ASME B36.10M schedule 20 dimensions.
SizeDNOutside diameterWall thicknessInside diameterWeight, emptyWater (US gal/ft)This size
NPS 8DN 2008.625219.07 mm0.2506.35 mm8.125206.38 mm22.3833.31 kg/m2.693all schedules →
NPS 10DN 25010.750273.05 mm0.2506.35 mm10.250260.35 mm28.0641.76 kg/m4.287all schedules →
NPS 12DN 30012.750323.85 mm0.2506.35 mm12.250311.15 mm33.4149.71 kg/m6.123all schedules →
NPS 14DN 35014.000355.60 mm0.3127.92 mm13.376339.75 mm45.6567.94 kg/m7.300all schedules →
NPS 16DN 40016.000406.40 mm0.3127.92 mm15.376390.55 mm52.3277.87 kg/m9.646all schedules →
NPS 18DN 45018.000457.20 mm0.3127.92 mm17.376441.35 mm58.9987.79 kg/m12.319all schedules →
NPS 20DN 50020.000508.00 mm0.3759.52 mm19.250488.95 mm78.67117.08 kg/m15.119all schedules →
NPS 22DN 55022.000558.80 mm0.3759.52 mm21.250539.75 mm86.69129.01 kg/m18.424all schedules →
NPS 24DN 60024.000609.60 mm0.3759.52 mm23.250590.55 mm94.71140.94 kg/m22.055all schedules →
NPS 26DN 65026.000660.40 mm0.50012.70 mm25.000635.00 mm136.30202.83 kg/m25.500all schedules →
NPS 28DN 70028.000711.20 mm0.50012.70 mm27.000685.80 mm146.99218.74 kg/m29.743all schedules →
NPS 30DN 75030.000762.00 mm0.50012.70 mm29.000736.60 mm157.68234.65 kg/m34.313all schedules →
NPS 32DN 80032.000812.80 mm0.50012.70 mm31.000787.40 mm168.37250.56 kg/m39.209all schedules →
NPS 34DN 85034.000863.60 mm0.50012.70 mm33.000838.20 mm179.06266.47 kg/m44.431all schedules →
NPS 36DN 90036.000914.40 mm0.50012.70 mm35.000889.00 mm189.75282.37 kg/m49.980all schedules →

Weight is plain-end carbon steel, w = 10.69 × t × (OD − t) lb/ft.

How the wall changes with size

The wall in schedule 20 is 0.250 in (6.3 mm) at NPS 8 and 0.500 in (12.7 mm) at NPS 36. Measured against the pipe it belongs to, that is 2.9% of the outside diameter at the small end and 1.4% at the large end, so the wall does not keep pace with the diameter. The pressure the pipe will hold moves the same way. On the basis used throughout this site (ASME B31.3, S = 20,000 psi, nominal wall, no corrosion allowance) schedule 20 holds about 1,187 psig at NPS 8 and about 562 psig at NPS 36. A schedule is therefore chosen size by size, from a calculation, and not once for a whole plant.

From NPS 26 up to NPS 36 the wall is the same in every size, 0.500 in (12.7 mm). Over that range schedule 20 is a fixed thickness and no longer a series that climbs with the size.

In this schedule the wall thickness coincides with STD in NPS 20 through NPS 24 and XS in NPS 26 through NPS 36. Outside those sizes it does not, so never substitute one designation for the other without checking the number.

Guides and comparisons for this page

What a pipe schedule actually isWhy a schedule is a wall series and not a thickness.Pipe wall thickness calculationBarlow and ASME B31.3, corrosion allowance and mill tolerance.Pipe sizing by flow rate and velocityTurn a flow rate into a line size using velocity limits.

Common questions

What sizes is schedule 20 pipe made in?

ASME B36.10M publishes schedule 20 in 15 sizes, from NPS 8 through NPS 36. Wall thickness runs from 0.250 in (6.3 mm) at the small end to 0.500 in (12.7 mm) at the large end.

Does schedule 20 mean the same wall thickness in every size?

No. It is a series, not a thickness. The wall is 0.250 in (6.3 mm) at NPS 8 and 0.500 in (12.7 mm) at NPS 36, so the thickness always has to be read off the table for the size in hand.

How pipe schedules work →