Pipe Schedule Chart — Sch 40/80/160 OD, ID & Wall (Steel, PVC, Copper)
Pipe schedule tables with OD, wall, and computed ID: steel NPS 1/8–12 per ASME B36.10M, PVC Sch 40/80 per ASTM D1785, and copper Type K/L/M per ASTM B88.
Updated August 16, 2026
Nominal pipe size (NPS) is a name, not a measurement: every NPS has one fixed outside diameter regardless of schedule, and increasing the schedule number thickens the wall inward. A 2-inch pipe is always 2.375 in OD; what changes between Sch 40, Sch 80, and Sch 160 is the bore. That is why fittings interchange across schedules but flow capacity does not.
The inside diameters below are computed as ID = OD − 2 × wall from the published OD and wall values — the same arithmetic a fabricator uses — rather than copied from a table, and a test recomputes every ID cell. For PVC, ASTM D1785 publishes minimum walls (tolerances are plus-side only), so the computed ID is the maximum bore; actual average bore runs slightly smaller. Copper tube uses a different system entirely: the OD is always nominal size plus 1/8 in, and the type letter (K heaviest, L, M lightest) sets the wall.
Steel dimensions follow ASME B36.10M for welded and seamless wrought steel pipe. Note the historic quirks: Sch 40 matches "standard weight" (STD) only through NPS 10 — at NPS 12, STD stays 0.375 in while Sch 40 is 0.406 in — and Sch 160 does not exist below NPS 1/2 or for NPS 3-1/2.
Steel Pipe — Sch 40/80/160 (ASME B36.10M)
| NPS | OD (in) | Sch 40 wall (in) | Sch 40 ID (in) | Sch 80 wall (in) | Sch 80 ID (in) | Sch 160 wall (in) | Sch 160 ID (in) |
|---|---|---|---|---|---|---|---|
| 1/8" | 0.405 | 0.068 | 0.269 | 0.095 | 0.215 | — | — |
| 1/4" | 0.540 | 0.088 | 0.364 | 0.119 | 0.302 | — | — |
| 3/8" | 0.675 | 0.091 | 0.493 | 0.126 | 0.423 | — | — |
| 1/2" | 0.840 | 0.109 | 0.622 | 0.147 | 0.546 | 0.188 | 0.464 |
| 3/4" | 1.050 | 0.113 | 0.824 | 0.154 | 0.742 | 0.219 | 0.612 |
| 1" | 1.315 | 0.133 | 1.049 | 0.179 | 0.957 | 0.250 | 0.815 |
| 1-1/4" | 1.660 | 0.140 | 1.380 | 0.191 | 1.278 | 0.250 | 1.160 |
| 1-1/2" | 1.900 | 0.145 | 1.610 | 0.200 | 1.500 | 0.281 | 1.338 |
| 2" | 2.375 | 0.154 | 2.067 | 0.218 | 1.939 | 0.344 | 1.687 |
| 2-1/2" | 2.875 | 0.203 | 2.469 | 0.276 | 2.323 | 0.375 | 2.125 |
| 3" | 3.500 | 0.216 | 3.068 | 0.300 | 2.900 | 0.438 | 2.624 |
| 3-1/2" | 4.000 | 0.226 | 3.548 | 0.318 | 3.364 | — | — |
| 4" | 4.500 | 0.237 | 4.026 | 0.337 | 3.826 | 0.531 | 3.438 |
| 5" | 5.563 | 0.258 | 5.047 | 0.375 | 4.813 | 0.625 | 4.313 |
| 6" | 6.625 | 0.280 | 6.065 | 0.432 | 5.761 | 0.719 | 5.187 |
| 8" | 8.625 | 0.322 | 7.981 | 0.500 | 7.625 | 0.906 | 6.813 |
| 10" | 10.750 | 0.365 | 10.020 | 0.594 | 9.562 | 1.125 | 8.500 |
| 12" | 12.750 | 0.406 | 11.938 | 0.688 | 11.374 | 1.312 | 10.126 |
Nominal (average) walls per ASME B36.10M. Sch 160 is not produced below NPS 1/2 or for NPS 3-1/2. At NPS 12, Sch 40 (0.406 in) differs from STD (0.375 in).
PVC Pipe — Sch 40/80 (ASTM D1785)
| Nominal size | OD (in) | Sch 40 wall (in) | Sch 40 ID (in) | Sch 80 wall (in) | Sch 80 ID (in) |
|---|---|---|---|---|---|
| 1/2" | 0.840 | 0.109 | 0.622 | 0.147 | 0.546 |
| 3/4" | 1.050 | 0.113 | 0.824 | 0.154 | 0.742 |
| 1" | 1.315 | 0.133 | 1.049 | 0.179 | 0.957 |
| 1-1/4" | 1.660 | 0.140 | 1.380 | 0.191 | 1.278 |
| 1-1/2" | 1.900 | 0.145 | 1.610 | 0.200 | 1.500 |
| 2" | 2.375 | 0.154 | 2.067 | 0.218 | 1.939 |
| 2-1/2" | 2.875 | 0.203 | 2.469 | 0.276 | 2.323 |
| 3" | 3.500 | 0.216 | 3.068 | 0.300 | 2.900 |
| 4" | 4.500 | 0.237 | 4.026 | 0.337 | 3.826 |
| 6" | 6.625 | 0.280 | 6.065 | 0.432 | 5.761 |
Minimum walls per ASTM D1785-12 Table 2 (iron-pipe-size ODs per Table 1; wall tolerance is plus-only, so the computed ID is the maximum bore). D1785 rounds a few large-size walls differently from steel — e.g. 10" and 12" Sch 80 are 0.593/0.687 in versus steel’s 0.594/0.688 in.
Copper Tube — Types K, L, M (ASTM B88)
| Nominal size | OD (in) | Type K wall (in) | Type K ID (in) | Type L wall (in) | Type L ID (in) | Type M wall (in) | Type M ID (in) |
|---|---|---|---|---|---|---|---|
| 1/4" | 0.375 | 0.035 | 0.305 | 0.030 | 0.315 | — | — |
| 3/8" | 0.500 | 0.049 | 0.402 | 0.035 | 0.430 | 0.025 | 0.450 |
| 1/2" | 0.625 | 0.049 | 0.527 | 0.040 | 0.545 | 0.028 | 0.569 |
| 3/4" | 0.875 | 0.065 | 0.745 | 0.045 | 0.785 | 0.032 | 0.811 |
| 1" | 1.125 | 0.065 | 0.995 | 0.050 | 1.025 | 0.035 | 1.055 |
| 1-1/4" | 1.375 | 0.065 | 1.245 | 0.055 | 1.265 | 0.042 | 1.291 |
| 1-1/2" | 1.625 | 0.072 | 1.481 | 0.060 | 1.505 | 0.049 | 1.527 |
| 2" | 2.125 | 0.083 | 1.959 | 0.070 | 1.985 | 0.058 | 2.009 |
| 2-1/2" | 2.625 | 0.095 | 2.435 | 0.080 | 2.465 | 0.065 | 2.495 |
| 3" | 3.125 | 0.109 | 2.907 | 0.090 | 2.945 | 0.072 | 2.981 |
| 4" | 4.125 | 0.134 | 3.857 | 0.110 | 3.905 | 0.095 | 3.935 |
Copper water tube OD = nominal size + 1/8 in for every type. Type M is not produced in 1/4 in. Type K is the heaviest wall (underground service), L is standard for pressurized plumbing, M for light-duty water distribution where codes allow.
Sources & Further Reading
- ASME B36.10M — Welded and Seamless Wrought Steel Pipe (ODs and nominal walls; verified across two independent tabulations)
- ASTM D1785-12 — PVC Plastic Pipe, Schedules 40, 80, and 120, Tables 1 & 2 (read directly from the standard)
- ASTM B88 — Seamless Copper Water Tube, Type K/L/M nominal walls (verified across two independent tabulations)
Frequently Asked Questions
Why is the inside diameter of Sch 40 pipe not the nominal size?
NPS was standardized around 19th-century wrought-iron walls, and the OD was frozen so threads and fittings stay interchangeable. For NPS 1/8 through 12 the OD exceeds the nominal name (a 1" pipe is 1.315 in OD), and the bore lands near — but not at — the nominal size. Only from NPS 14 upward does OD equal the nominal size exactly.
Is Schedule 40 the same as standard weight (STD)?
Through NPS 10, yes — the walls coincide. At NPS 12, STD keeps a 0.375 in wall while Sch 40 steps up to 0.406 in, and the two series continue to diverge in larger sizes. If a drawing says STD above NPS 10, do not silently substitute Sch 40.
Do PVC and steel pipe of the same schedule have the same dimensions?
ASTM D1785 deliberately adopts iron-pipe-size ODs and schedule walls, so PVC Sch 40 mates dimensionally with steel Sch 40. The fine print: D1785 publishes walls as minimums with plus-only tolerance (steel walls are nominal with ±12.5% tolerance), and a couple of large sizes round one mil differently, so IDs are close but not byte-identical.
Which copper type do I need — K, L, or M?
Same OD, different wall. Type K (thickest) is typical for underground water service, Type L is the general-purpose choice for pressurized supply lines, and Type M (thinnest) is limited to interior distribution where the local code accepts it. Fittings fit all three because the OD never changes.
Try the Calculators
Pipe Schedule Chart — Sch 40/80/160 OD, ID & Wall (Steel, PVC, Copper) — reuven.tools/reference/pipe-schedules — verified against: ASME B36.10M — Welded and Seamless Wrought Steel Pipe (ODs and nominal walls; verified across two independent tabulations); ASTM D1785-12 — PVC Plastic Pipe, Schedules 40, 80, and 120, Tables 1 & 2 (read directly from the standard); ASTM B88 — Seamless Copper Water Tube, Type K/L/M nominal walls (verified across two independent tabulations)