Sch 20 Pipe Dimensions

Sch 20 pipe dimensions vary with the nominal pipe size. Schedule 20 defines a specific wall thickness for each applicable NPS size, while the outside diameter is set by the nominal pipe size standard.For carbon and alloy steel pipe, ASME B36.10 provides standardized dimensions for welded and seamless wrought steel pipe. The standard covers pipe dimensions, wall thicknesses and weights for piping applications.
The table below gives the most useful information for purchasing, engineering and fabrication:
NPS
DN
Outside diameter (OD)
Inside diameter (ID)
Wall thickness
Weight per foot
Weight per meter
Important: In ASME B36.10 dimension tables, Schedule 20 is generally listed from NPS 8 through NPS 36. Many online charts incorrectly label thin-wall dimensions for smaller sizes as Schedule 20. Always check the applicable standard before ordering.

The following is the sch20 size specification table

Sch 20 Pipe Size Chart

The following chart summarizes commonly specified ASME B36.10 Schedule 20 steel pipe dimensions.

Nominal size [inches]	Outside diameter [inches]	Outside diameter [mm]	Wall thickness [inches]	Wall thickness [mm]	Weight [lb/ft]	Weight [kg/m]
8 inches	8.625 inches	219.1 mm	0.250 inches	6.35 mm	22.36 lb/ft	33.31 kg/m
10 inches	10.750 inches	273.0 mm	0.250 inches	6.35 mm	28.04 lb/ft	41.77 kg/m
12 inches	12.750 inches	323.8 mm	0.250 inches	6.35 mm	33.38 lb/ft	49.73 kg/m
14 inches	14.000 inches	355.6 mm	0.312 inches	7.92 mm	45.61 lb/ft	67.90 kg/m
16 inches	16.000 inches	406.4 mm	0.312 inches	7.92 mm	52.27 lb/ft	77.83 kg/m
18 inches	18.000 inches	457.0 mm	0.312 inches	7.92 mm	58.94 lb/ft	87.71 kg/m
20 inches	20.000 inches	508.0 mm	0.375 inches	9.53 mm	78.60 lb/ft	117.15 kg/m
22 inches	22.000 inches	559.0 mm	0.375 inches	9.53 mm	86.61 lb/ft	129.13 kg/m
24 inches	24.000 inches	610.0 mm	0.375 inches	9.53 mm	94.62 lb/ft	141.12 kg/m
26 inches	26.000 inches	660.0 mm	0.500 inches	12.70 mm	136.17 lb/ft	202.72 kg/m
28 inches	28.000 inches	711.0 mm	0.500 inches	12.70 mm	146.85 lb/ft	218.69 kg/m
30 inches	30.000 inches	762.0 mm	0.500 inches	12.70 mm	157.53 lb/ft	234.67 kg/m
32 inches	32.000 inches	813.0 mm	0.500 inches	12.70 mm	168.21 lb/ft	250.64 kg/m
34 inches	34.000 inches	864.0 mm	0.500 inches	12.70 mm	178.89 lb/ft	266.61 kg/m
36 inches	36.000 inches	914.0 mm	0.500 inches	12.70 mm	189.57 lb/ft	282.27 kg/m

The core dimensions above are consistent with published ASME B36.10-based Schedule 20 tables. For example, NPS 8 has a 219.1 mm OD and 6.35 mm wall, while NPS 20 has a 508 mm OD and 9.53 mm wall.

Note: Weight figures are nominal plain-end steel pipe weights. Actual supplied weight can vary with manufacturing tolerances, pipe length, end finish and material density.

Expression method of steel pipe wall thickness:

(3) The pipe wall thickness is expressed by the pipe weight, it divides the pipe wall thickness into three types: a. Standard weight pipe, indicated by STD b. Thickened pipe, indicated by XS c. Extra thick pipe, indicated by XXS. For pipes with DN≤250mm, Sch40 is equivalent to STD, and for pipes with DN<200mm, Sch80 is equivalent to XS.

Schedule 20 Pipe Outside Diameter

The outside diameter (OD) is determined by the nominal pipe size.

NPS	OD
8	8.625 in / 219.1 mm
10	10.750 in / 273.0 mm
12	12.750 in / 323.8 mm
16	16.000 in / 406.4 mm
20	20.000 in / 508.0 mm
24	24.000 in / 610.0 mm
36	36.000 in / 914.4 mm

A common mistake is assuming that the NPS number equals the actual OD.That is not true for many pipe sizes.NPS 8 does not have an 8.000-inch OD.Its standardized OD is 8.625 inches.ASME notes that NPS 12 and smaller have outside diameters numerically larger than their nominal size.

Schedule 20 Pipe Inside Diameter

The inside diameter is calculated from the outside diameter and wall thickness:
ID = OD − 2 × Wall Thickness
For example, take an NPS 20 Schedule 20 pipe:
OD = 20.000 in
Wall thickness = 0.375 in
Therefore:
ID = 20.000 − 2 × 0.375
ID = 19.250 in
That equals approximately 488.9 mm.

This is why the ID changes when the schedule changes, even though the OD of a given NPS normally remains the same.

Schedule 20 Pipe Dimensions in mm

If your customer gives the pipe size in inches, use NPS and DN together when preparing a quotation.
Common Schedule 20 conversions include:

NPS	DN	OD
8	DN200	219.1 mm
10	DN250	273.0 mm
12	DN300	323.8 mm
14	DN350	355.6 mm
16	DN400	406.4 mm
18	DN450	457.0 mm
20	DN500	508.0 mm
22	DN550	559.0 mm
24	DN600	610.0 mm
26	DN650	660.4 mm
28	DN700	711.2 mm
30	DN750	762.0 mm
32	DN800	812.8 mm
34	DN850	863.6 mm
36	DN900	914.4 mm

NPS and DN are nominal designations. They should not be treated as direct inch-to-millimeter conversions.

FAQ

What does Sch 20 mean?
Sch 20 means Schedule 20, a standardized pipe wall-thickness designation. The actual wall thickness depends on the nominal pipe size.

What is the wall thickness of Schedule 20 pipe?
For ASME B36.10 large-bore Schedule 20 pipe, the wall thickness ranges from approximately 0.250 in (6.35 mm) for NPS 8–12 to 0.500 in (12.70 mm) for NPS 26–36.

What is the OD of NPS 8 Schedule 20 pipe?
NPS 8 Schedule 20 pipe has an outside diameter of 8.625 inches (219.1 mm).

What is the ID of NPS 20 Schedule 20 pipe?
NPS 20 Sch 20 has an approximate inside diameter of 19.250 inches (488.9 mm). Its OD is 20.000 inches and its nominal wall thickness is 0.375 inches.

How much does Schedule 20 pipe weigh?
The weight depends on pipe size. For example, NPS 8 weighs about 22.36 lb/ft (33.31 kg/m), while NPS 20 weighs about 78.60 lb/ft (117.15 kg/m).

Conclusion

Sch 20 pipe dimensions are determined by the nominal pipe size and the applicable Schedule 20 wall thickness.For ASME B36.10 steel pipe, the commonly referenced Schedule 20 range starts at NPS 8. The OD is standardized by NPS, while the wall thickness and resulting ID vary by schedule and size.
For quick reference:
ID = OD − 2 × Wall Thickness
When ordering Schedule 20 pipe, do not specify the schedule alone. Confirm the NPS, DN, OD, wall thickness, material grade, manufacturing method, length, end finish and applicable standard.
This approach reduces the risk of ordering a pipe with the wrong wall thickness or dimensional designation.