Schedule 40 Pipes Thickness Chart

Schedule 40 pipe is widely used in industrial, commercial, mechanical, and piping applications. However, Schedule 40 does not refer to one fixed pipe wall thickness.The actual wall thickness depends on the pipe's nominal pipe size (NPS). For example, a 2-inch Schedule 40 pipe has a 0.154-inch wall, while a 6-inch Schedule 40 pipe has a 0.280-inch wall.This guide provides a practical Schedule 40 pipe thickness chart with outside diameter (OD), inside diameter (ID), and nominal wall thickness. It also explains how Schedule 40 dimensions work and how to select the correct pipe thickness for a project.

Schedule 40 Pipe Thickness Chart

The table below shows common Schedule 40 steel pipe dimensions. The dimensions follow the standard pipe sizing system used for steel pipe, with thickness shown in both inches and millimeters.

NPS	Outside Diameter (OD)	OD (mm)	Schedule 40 Wall Thickness	Wall Thickness (mm)	Approx. ID
1/8	0.405 in	10.3 mm	0.068 in	1.73 mm	0.269 in
1/4	0.540 in	13.7 mm	0.088 in	2.24 mm	0.364 in
3/8	0.675 in	17.1 mm	0.091 in	2.31 mm	0.493 in
1/2	0.840 in	21.3 mm	0.083 in	2.11 mm	0.674 in
3/4	1.050 in	26.7 mm	0.083 in	2.11 mm	0.884 in
1	1.315 in	33.4 mm	0.109 in	2.77 mm	1.097 in
1-1/4	1.660 in	42.2 mm	0.140 in	3.56 mm	1.380 in
1-1/2	1.900 in	48.3 mm	0.145 in	3.68 mm	1.610 in
2	2.375 in	60.3 mm	0.154 in	3.91 mm	2.067 in
2-1/2	2.875 in	73.0 mm	0.203 in	5.16 mm	2.469 in
3	3.500 in	88.9 mm	0.216 in	5.49 mm	3.068 in
3-1/2	4.000 in	101.6 mm	0.226 in	5.74 mm	3.548 in
4	4.500 in	114.3 mm	0.237 in	6.02 mm	4.026 in
5	5.563 in	141.3 mm	0.258 in	6.55 mm	5.047 in
6	6.625 in	168.3 mm	0.280 in	7.11 mm	6.065 in
8	8.625 in	219.1 mm	0.322 in	8.18 mm	7.981 in
10	10.750 in	273.1 mm	0.365 in	9.27 mm	10.020 in
12	12.750 in	323.9 mm	0.375 in	9.53 mm	12.000 in
14	14.000 in	355.6 mm	0.375 in	9.53 mm	13.250 in
16	16.000 in	406.4 mm	0.375 in	9.53 mm	15.250 in
18	18.000 in	457.2 mm	0.375 in	9.53 mm	17.250 in
20	20.000 in	508.0 mm	0.375 in	9.53 mm	19.250 in
24	24.000 in	610.0 mm	0.375 in	9.53 mm	23.250 in

Note: OD and nominal wall thickness are standardized dimensions. Actual measured wall thickness can vary because of manufacturing tolerances.For project procurement, always confirm the applicable dimensional standard and material specification before ordering.

Schedule 40 Pipe Thickness in mm

Many international projects specify pipe dimensions in millimeters.
The conversion is straightforward:
Wall Thickness (mm) = Wall Thickness (in) × 25.4

For example:
2-inch SCH 40:
0.154 × 25.4 = 3.91 mm
Therefore, the nominal wall thickness of 2-inch Schedule 40 steel pipe is approximately 3.91 mm.
However, do not round the value too early when preparing engineering calculations. Use the applicable standard's nominal dimensions and tolerances for final design and inspection.

Schedule 40 Pipe OD and ID
Wall thickness is closely related to the pipe's outside and inside diameters.
The approximate inside diameter can be calculated as:
ID = OD − 2 × Wall Thickness
For example, an NPS 2 Schedule 40 pipe has:
OD = 2.375 in
Wall thickness = 0.154 in
Therefore:
ID = 2.375 − (2 × 0.154)
ID = 2.067 in
This explains why the nominal pipe size should not be confused with the actual outside or inside diameter.
An NPS 2 pipe does not have an actual OD of 2 inches. Its standardized OD is 2.375 inches.

Schedule 40 vs Schedule 80 Pipe Thickness

Schedule 40 and Schedule 80 can have the same nominal pipe size and outside diameter but different wall thicknesses.

NPS	SCH 40 Wall	SCH 80 Wall
1 inch	0.109 in	0.179 in
2 inch	0.154 in	0.218 in
3 inch	0.216 in	0.300 in
4 inch	0.237 in	0.337 in
6 inch	0.280 in	0.432 in
8 inch	0.322 in	0.500 in

Schedule 40 Pipe Thickness vs Actual Measured Thickness

The thickness shown in a Schedule 40 chart is the nominal wall thickness.It should not be interpreted as the exact thickness at every point on a finished pipe.During manufacturing, wall thickness can vary within the tolerance allowed by the applicable product standard.
For example, a pipe specified as:
NPS 2 SCH 40
has a nominal wall thickness of:
0.154 in (3.91 mm)
Inspection measurements may show values slightly different from the nominal dimension.

For procurement and inspection, the applicable standard's dimensional tolerance should be used to determine whether the measured pipe meets the requirement.

Conclusion

Schedule 40 pipe does not have one fixed wall thickness.The required thickness depends on the nominal pipe size. For example, NPS 2 Schedule 40 pipe has a 0.154-inch wall, while NPS 6 has a 0.280-inch wall.For accurate pipe selection, check the NPS, OD, wall thickness, ID, material grade, and applicable standard together.If you are sourcing Schedule 40 steel pipe, providing the complete specification helps ensure the supplied pipe matches your project requirements.

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