PEX & CPVC Tubing Size Chart — OD, Wall & ID per ASTM F876 / D2846
PEX and CPVC tubing dimensions: OD, wall, and computed ID for ASTM F876 SDR9 PEX and ASTM D2846 SDR11 CPVC in copper tube sizes.
Updated August 22, 2026
PEX and CPVC water-distribution tubing both borrow the copper tube size (CTS) system: the outside diameter is always the nominal size plus 1/8 inch, exactly like copper tube — which is why a 1/2″ PEX fitting, a 1/2″ CPVC tube, and 1/2″ copper all measure 0.625 in across. Wall thickness then follows a standard dimension ratio (SDR): PEX per ASTM F876 holds OD ÷ wall = 9, and CPVC CTS per ASTM D2846 holds OD ÷ wall = 11. A constant SDR means constant pressure rating across sizes — every diameter of D2846 CPVC carries the same 100 psi at 180 °F rating, and F876 PEX the same 160 psi at 73 °F class.
Two systematic quirks are worth knowing before you take a caliper to the table. First, the smallest sizes are thicker than the SDR predicts: the standards impose a minimum-wall floor (0.070 in for F876 PEX at 3/8″ and 1/2″; 0.068 in for D2846 CPVC at 1/2″), so those rows are the floor in action, not rounding errors. Second, the ID column here is computed as OD − 2 × minimum wall; manufacturer sheets print a slightly smaller "nominal ID" based on the average wall the extruder actually targets (minimum plus half the plus-tolerance). PEX also flows differently than its ID suggests because fittings are insert-style and neck the bore down — a design difference from CPVC’s socket fittings, covered in the FAQ.
PEX Tubing — ASTM F876, CTS SDR9
| Nominal size | OD (in) | Min wall (in) | ID, computed (in) |
|---|---|---|---|
| 3/8″ | 0.500 | 0.070 | 0.360 |
| 1/2″ | 0.625 | 0.070 | 0.485 |
| 5/8″ | 0.750 | 0.083 | 0.584 |
| 3/4″ | 0.875 | 0.097 | 0.681 |
| 1″ | 1.125 | 0.125 | 0.875 |
| 1-1/4″ | 1.375 | 0.153 | 1.069 |
| 1-1/2″ | 1.625 | 0.181 | 1.263 |
| 2″ | 2.125 | 0.236 | 1.653 |
OD = nominal + 1/8″; wall = OD ÷ 9 except the 3/8″ and 1/2″ rows, where the standard’s 0.070 in minimum-wall floor governs. ID computed from minimum wall; manufacturers print nominal IDs ~0.010 in smaller (average-wall basis). Applies equally to PEX-A/B/C — the dimensions come from F876, not the crosslinking method.
CPVC Tubing — ASTM D2846, CTS SDR11
| Nominal size | OD (in) | Min wall (in) | ID, computed (in) |
|---|---|---|---|
| 1/2″ | 0.625 | 0.068 | 0.489 |
| 3/4″ | 0.875 | 0.080 | 0.715 |
| 1″ | 1.125 | 0.102 | 0.921 |
| 1-1/4″ | 1.375 | 0.125 | 1.125 |
| 1-1/2″ | 1.625 | 0.148 | 1.329 |
| 2″ | 2.125 | 0.193 | 1.739 |
OD = nominal + 1/8″; wall = OD ÷ 11 except the 1/2″ row, where the 0.068 in minimum-wall floor governs. Rating: 100 psi @ 180 °F / 400 psi @ 73 °F, all sizes (constant SDR). CPVC also ships as IPS Schedule 40/80 pipe per ASTM F441 — different OD system entirely; see the pipe schedules chart.
Sources & Further Reading
- ASTM F876 dimension table as reproduced in Viega published tech data (Barrier PEX TD-HC 0821; PureFlow TD-PF 0123) and the Engineering ToolBox ASTM F876 PEX tube dimensions page (independent cross-check of every OD/wall cell); IWISS F876 technical specifications as third check
- ASTM D2846 dimension table as reproduced in the Charlotte Pipe FlowGuard Gold CPVC CTS submittal package (SUB-PAC-FGG, 2025) and the Spears EverTUFF CTS CPVC technical data page (independent cross-check of every OD/wall cell)
- IDs computed as OD − 2 × minimum wall; CTS identity OD = nominal + 1/8 in (both test-enforced, never transcribed)
Frequently Asked Questions
Why is the OD of 1/2″ PEX the same as 1/2″ copper?
Both live in the copper tube size system: OD = nominal + 1/8 in, so 1/2″ anything-CTS measures 0.625 in outside. That shared OD is what makes push-fit fittings work across copper, PEX, and CPVC with one body. It does NOT mean the IDs match — 1/2″ copper type L has a 0.545 in bore while 1/2″ PEX computes to 0.485 in, because PEX carries an SDR9 wall.
Does 1/2″ PEX really flow that much less than 1/2″ copper?
Yes, and fittings make it worse. The tube bore is already smaller (0.485 vs 0.545 in computed), but PEX insert fittings sit INSIDE the tube, necking each crimp or expansion joint down further — a 1/2″ crimp insert bore runs near 3/8 in. CPVC avoids this with socket fittings that wrap the outside. The practical rule plumbers follow: home-run 1/2″ PEX to a manifold, or upsize to 3/4″ where a branch feeds multiple fixtures.
Why are the smallest sizes thicker than SDR9/SDR11 predicts?
Because a pure ratio would give impractically thin walls at small diameters — SDR9 on a 1/2″ (0.625 OD) tube computes to 0.069 in, and SDR11 CPVC would drop to 0.057 in. Both standards impose a minimum-wall floor instead: 0.070 in for F876 PEX, 0.068 in for D2846 CPVC. Those floor rows are marginally stronger than the SDR rating requires; everything 5/8″ and up tracks the ratio within rounding.
Is this the same CPVC as the yellow-tinted Schedule 80 pipe at the supply house?
Different product family. This chart is CTS CPVC (ASTM D2846): copper tube ODs, SDR11 wall, tan color, rated 100 psi at 180 °F for domestic water. Schedule 40/80 CPVC (ASTM F441) uses iron pipe size ODs and schedule walls, and is a commercial/industrial system rated by size. The two do not interchange — fittings, cements, and dimensions all differ. PEX-AL-PEX composite tubing (ASTM F1281) is a third system again, with its own metric-leaning dimensions.
Try the Calculators
PEX & CPVC Tubing Size Chart — OD, Wall & ID per ASTM F876 / D2846 — reuven.tools/reference/pex-cpvc-dimensions — verified against: ASTM F876 dimension table as reproduced in Viega published tech data (Barrier PEX TD-HC 0821; PureFlow TD-PF 0123) and the Engineering ToolBox ASTM F876 PEX tube dimensions page (independent cross-check of every OD/wall cell); IWISS F876 technical specifications as third check; ASTM D2846 dimension table as reproduced in the Charlotte Pipe FlowGuard Gold CPVC CTS submittal package (SUB-PAC-FGG, 2025) and the Spears EverTUFF CTS CPVC technical data page (independent cross-check of every OD/wall cell); IDs computed as OD − 2 × minimum wall; CTS identity OD = nominal + 1/8 in (both test-enforced, never transcribed)