Steel (ASME B36.10M) vs PVC (ASTM D2241)
Is PVC the same size as steel pipe? — the short answer is that a name is not a measurement. Of the 9 nominal sizes both standards cover, 9 share the same outer diameter and 0 do not.
- Shared sizes
- 9
- Same OD
- 9
- Different OD
- 0
- Only in steel
- 8
| Nominal | ASME B36.10M OD (in) | ASME B36.10M OD (mm) | ASTM D2241 OD (in) | ASTM D2241 OD (mm) | Same outside? | steel walls | PVC walls |
|---|---|---|---|---|---|---|---|
| 1/2 | 0.840 | 21.336 | 0.840 | 21.336 | yes | Sch 10 0.083, Sch 40 0.109, Sch 80 0.147, Sch 160 0.188, STD 0.109, XS 0.147, XXS 0.294 | Sch 40 0.109, Sch 80 0.147 |
| 3/4 | 1.050 | 26.67 | 1.050 | 26.67 | yes | Sch 10 0.083, Sch 40 0.113, Sch 80 0.154, Sch 160 0.219, STD 0.113, XS 0.154, XXS 0.308 | Sch 40 0.113, Sch 80 0.154 |
| 1 | 1.315 | 33.401 | 1.315 | 33.401 | yes | Sch 10 0.109, Sch 40 0.133, Sch 80 0.179, Sch 160 0.250, STD 0.133, XS 0.179, XXS 0.358 | Sch 40 0.133, Sch 80 0.179 |
| 1 1/2 | 1.900 | 48.26 | 1.900 | 48.26 | yes | Sch 10 0.109, Sch 40 0.145, Sch 80 0.200, Sch 160 0.281, STD 0.145, XS 0.200, XXS 0.400 | Sch 40 0.145, Sch 80 0.200 |
| 2 | 2.375 | 60.325 | 2.375 | 60.325 | yes | Sch 10 0.109, Sch 40 0.154, Sch 80 0.218, Sch 160 0.344, STD 0.154, XS 0.218, XXS 0.436 | Sch 40 0.154, Sch 80 0.218 |
| 3 | 3.500 | 88.9 | 3.500 | 88.9 | yes | Sch 10 0.120, Sch 40 0.216, Sch 80 0.300, Sch 160 0.438, STD 0.216, XS 0.300, XXS 0.600 | Sch 40 0.216, Sch 80 0.300 |
| 4 | 4.500 | 114.3 | 4.500 | 114.3 | yes | Sch 10 0.120, Sch 40 0.237, Sch 80 0.337, Sch 120 0.438, Sch 160 0.531, STD 0.237, XS 0.337, XXS 0.674 | Sch 40 0.237, Sch 80 0.337 |
| 6 | 6.625 | 168.275 | 6.625 | 168.275 | yes | Sch 10 0.134, Sch 40 0.280, Sch 80 0.432, Sch 120 0.562, Sch 160 0.719, STD 0.280, XS 0.432, XXS 0.864 | Sch 40 0.280, Sch 80 0.432 |
| 8 | 8.625 | 219.075 | 8.625 | 219.075 | yes | Sch 10 0.148, Sch 20 0.250, Sch 30 0.277, Sch 40 0.322, Sch 60 0.406, Sch 80 0.500, Sch 100 0.594, Sch 120 0.719, Sch 140 0.812, Sch 160 0.906, STD 0.322, XS 0.500, XXS 0.875 | Sch 40 0.322, Sch 80 0.500 |
Sizes one standard covers and the other does not
Steel only: 1/8 (0.405 in / 10.287 mm) · 1/4 (0.540 in / 13.716 mm) · 3/8 (0.675 in / 17.145 mm) · 1 1/4 (1.660 in / 42.164 mm) · 2 1/2 (2.875 in / 73.025 mm) · 5 (5.563 in / 141.3 mm) · 10 (10.750 in / 273.05 mm) · 12 (12.750 in / 323.85 mm)
Why the two do not line up
steel and PVC sizes come from different habits of naming. Where the plastic standard grew out of “iron pipe size”, the OD is deliberately the steel OD so that fittings share a footprint; where it grew out of tubing practice, the OD is its own number and the nominal size is closer to the bore. Nothing in the name tells you which case you are in — the table does.
Full lists: ASME B36.10M chart · ASTM D2241 chart. Each size page lists the sources for its own numbers.