Pipe Size Chart in mm and Inches
Quick answer: nominal pipe size is not the same as outside diameter. For example, 1/2 in NPS pipe has a 0.840 in outside diameter, which is about 21.3 mm. DN is a metric designator, not a direct inside-diameter measurement.
NPS To DN Pipe Size Chart
| NPS size | DN size | Outside diameter | Outside diameter mm | Sch 40 wall approx. |
|---|---|---|---|---|
| 1/8 in | DN 6 | 0.405 in | 10.3 mm | 0.068 in / 1.73 mm |
| 1/4 in | DN 8 | 0.540 in | 13.7 mm | 0.088 in / 2.24 mm |
| 3/8 in | DN 10 | 0.675 in | 17.1 mm | 0.091 in / 2.31 mm |
| 1/2 in | DN 15 | 0.840 in | 21.3 mm | 0.109 in / 2.77 mm |
| 3/4 in | DN 20 | 1.050 in | 26.7 mm | 0.113 in / 2.87 mm |
| 1 in | DN 25 | 1.315 in | 33.4 mm | 0.133 in / 3.38 mm |
| 1-1/4 in | DN 32 | 1.660 in | 42.2 mm | 0.140 in / 3.56 mm |
| 1-1/2 in | DN 40 | 1.900 in | 48.3 mm | 0.145 in / 3.68 mm |
| 2 in | DN 50 | 2.375 in | 60.3 mm | 0.154 in / 3.91 mm |
| 2-1/2 in | DN 65 | 2.875 in | 73.0 mm | 0.203 in / 5.16 mm |
| 3 in | DN 80 | 3.500 in | 88.9 mm | 0.216 in / 5.49 mm |
| 4 in | DN 100 | 4.500 in | 114.3 mm | 0.237 in / 6.02 mm |
| 6 in | DN 150 | 6.625 in | 168.3 mm | 0.280 in / 7.11 mm |
| 8 in | DN 200 | 8.625 in | 219.1 mm | 0.322 in / 8.18 mm |
| 10 in | DN 250 | 10.750 in | 273.1 mm | 0.365 in / 9.27 mm |
| 12 in | DN 300 | 12.750 in | 323.9 mm | 0.406 in / 10.31 mm |
Pipe Size Terms
- NPS: nominal pipe size, used for inch pipe names.
- DN: metric nominal designation paired with NPS sizes.
- OD: outside diameter, the dimension you can measure across the pipe.
- Schedule: wall thickness family, such as Schedule 40 or Schedule 80.
Related references: PVC pipe sizes chart, PEX tubing size chart, and EMT conduit sizes chart.
Source Notes
Dimensions were checked against ASME B36.10/B36.19 style pipe dimension references including Octal Steel’s ANSI pipe dimension chart and Ferrobend’s ASME B36.10M dimension chart. Confirm material and schedule before ordering fittings.
