Schedule 40 Steel Pipe Size Chart
The Schedule 40 Size Chart provides the standard nominal pipe sizes, outside diameters, wall thicknesses, and related dimensions for Schedule 40 steel pipe. Schedule 40 is widely used for water piping, fire protection, HVAC systems, compressed air, industrial piping, and general mechanical applications.
For carbon and alloy steel pipe, Schedule 40 dimensions are standardized under ASME B36.10M. The nominal pipe size (NPS) identifies the pipe size, while the actual outside diameter (OD) varies according to the NPS rather than being equal to the nominal size.
The following table provides commonly used Schedule 40 pipe sizes from 1/8 inch to 24 inches.
| NPS | DN | OD (in) | OD (mm) | Wall Thickness (mm) | ID (mm) |
| 1/8″ | DN6 | 0.405 | 10.3 | 1.73 | 6.84 |
| 1/4″ | DN8 | 0.54 | 13.7 | 2.24 | 9.22 |
| 3/8″ | DN10 | 0.675 | 17.1 | 2.31 | 12.48 |
| 1/2″ | DN15 | 0.84 | 21.3 | 2.77 | 15.76 |
| 3/4″ | DN20 | 1.05 | 26.7 | 2.87 | 20.96 |
| 1″ | DN25 | 1.315 | 33.4 | 3.38 | 26.64 |
| 1-1/4″ | DN32 | 1.66 | 42.2 | 3.56 | 35.08 |
| 1-1/2″ | DN40 | 1.9 | 48.3 | 3.68 | 40.94 |
| 2″ | DN50 | 2.375 | 60.3 | 3.91 | 52.48 |
| 2-1/2″ | DN65 | 2.875 | 73 | 5.16 | 62.68 |
| 3″ | DN80 | 3.5 | 88.9 | 5.49 | 77.92 |
| 3-1/2″ | DN90 | 4 | 101.6 | 5.74 | 90.12 |
| 4″ | DN100 | 4.5 | 114.3 | 6.02 | 102.26 |
| 5″ | DN125 | 5.563 | 141.3 | 6.55 | 128.2 |
| 6″ | DN150 | 6.625 | 168.3 | 7.11 | 154.08 |
| 8″ | DN200 | 8.625 | 219.1 | 8.18 | 202.74 |
| 10″ | DN250 | 10.75 | 273.1 | 9.27 | 254.56 |
| 12″ | DN300 | 12.75 | 323.9 | 9.53 | 304.84 |
| 14″ | DN350 | 14 | 355.6 | 9.53 | 336.54 |
| 16″ | DN400 | 16 | 406.4 | 9.53 | 387.34 |
| 18″ | DN450 | 18 | 457.2 | 9.53 | 438.14 |
| 20″ | DN500 | 20 | 508 | 9.53 | 488.94 |
| 22″ | DN550 | 22 | 558.8 | 9.53 | 539.74 |
| 24″ | DN600 | 24 | 609.6 | 9.53 | 590.54 |
The table follows the standard Schedule 40 dimensional series for steel pipe. For engineering, fabrication, and purchasing, the applicable edition of the referenced standard should always be checked because dimensional requirements and product specifications should be confirmed against the project specification.
Schedule 40 Pipe Sizes in Inches and mm
Schedule 40 pipes are commonly specified using NPS in inches, while engineering drawings, fabrication documents, and international projects may also use millimetres.
| NPS | DN | Nominal Size (inches) | O.D. (in) | O.D. (mm) | Schedule 40 W.T. (in) | Schedule 40 W.T.(mm) | Inside Diameter (in) | Inside Diameter (mm) |
| 1/8″ | DN6 | 0.125 | 0.405 | 10.3 | 0.068 | 1.73 | 0.269 | 6.84 |
| 1/4″ | DN8 | 0.25 | 0.54 | 13.7 | 0.088 | 2.24 | 0.363 | 9.22 |
| 3/8″ | DN10 | 0.375 | 0.675 | 17.1 | 0.091 | 2.31 | 0.491 | 12.48 |
| 1/2″ | DN15 | 0.5 | 0.84 | 21.3 | 0.109 | 2.77 | 0.62 | 15.76 |
| 3/4″ | DN20 | 0.75 | 1.05 | 26.7 | 0.113 | 2.87 | 0.825 | 20.96 |
| 1″ | DN25 | 1 | 1.315 | 33.4 | 0.133 | 3.38 | 1.049 | 26.64 |
| 1-1/4″ | DN32 | 1.25 | 1.66 | 42.2 | 0.14 | 3.56 | 1.38 | 35.08 |
| 1-1/2″ | DN40 | 1.5 | 1.9 | 48.3 | 0.145 | 3.68 | 1.612 | 40.94 |
| 2″ | DN50 | 2 | 2.375 | 60.3 | 0.154 | 3.91 | 2.066 | 52.48 |
| 2-1/2″ | DN65 | 2.5 | 2.875 | 73 | 0.203 | 5.16 | 2.468 | 62.68 |
| 3″ | DN80 | 3 | 3.5 | 88.9 | 0.216 | 5.49 | 3.067 | 77.92 |
| 3-1/2″ | DN90 | 3.5 | 4 | 101.6 | 0.226 | 5.74 | 3.548 | 90.12 |
| 4″ | DN100 | 4 | 4.5 | 114.3 | 0.237 | 6.02 | 4.026 | 102.26 |
| 5″ | DN125 | 5 | 5.563 | 141.3 | 0.258 | 6.55 | 5.047 | 128.2 |
| 6″ | DN150 | 6 | 6.625 | 168.3 | 0.28 | 7.11 | 6.066 | 154.08 |
| 8″ | DN200 | 8 | 8.625 | 219.1 | 0.322 | 8.18 | 7.981 | 202.74 |
| 10″ | DN250 | 10 | 10.75 | 273.1 | 0.365 | 9.27 | 10.02 | 254.56 |
| 12″ | DN300 | 12 | 12.75 | 323.9 | 0.375 | 9.53 | 11.998 | 304.84 |
| 14″ | DN350 | 14 | 14 | 355.6 | 0.375 | 9.53 | 13.25 | 336.54 |
| 16″ | DN400 | 16 | 16 | 406.4 | 0.375 | 9.53 | 15.25 | 387.34 |
| 18″ | DN450 | 18 | 18 | 457.2 | 0.375 | 9.53 | 17.25 | 438.14 |
| 20″ | DN500 | 20 | 20 | 508 | 0.375 | 9.53 | 19.25 | 488.94 |
| 22″ | DN550 | 22 | 22 | 558.8 | 0.375 | 9.53 | 21.25 | 539.74 |
| 24″ | DN600 | 24 | 24 | 609.6 | 0.375 | 9.53 | 23.25 |
Values are based on standard Schedule 40 dimensions. Approximate inside diameters are calculated using the nominal outside diameter and wall thickness. Actual dimensions may vary according to the applicable standard and manufacturing tolerances.
NPS — Nominal Pipe Size
NPS (Nominal Pipe Size) is the standard designation used to identify pipe size in the inch-based system.
DN — Nominal Diameter
DN (Nominal Diameter) is the metric designation commonly used alongside NPS.
OD — Outside Diameter
OD (Outside Diameter) is the actual standardized external diameter of the pipe.The OD is particularly important when selecting compatible fittings, flanges, clamps, supports, and connections.
ID — Inside Diameter
ID (Inside Diameter) represents the internal bore of the pipe.Therefore, the ID determines the available internal flow area and is useful when evaluating flow capacity and pressure loss.
