1" PVC and steel pipe are 1.315" (33.4 mm) across the outside. 1" copper, PEX and CTS CPVC are 1.125", which is 1-1/8" (28.6 mm).
1 inch pipe sizes by type
1" pipe and tube: outside diameter, inside diameter and wall | Pipe | Outside (OD) | Inside (ID) | Wall |
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| PVC Schedule 40 | 1.315" (33.4 mm) | n/a | 0.133" |
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| PVC Schedule 80 | 1.315" (33.4 mm) | n/a | 0.179" |
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| CPVC Schedule 80 (Charlotte Corzan) | 1.315" (33.4 mm) | n/a | 0.179" |
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| Steel Schedule 40, black or galvanized | 1.315" (33.4 mm) | 1.049" | 0.133" |
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| Steel Schedule 80 | 1.315" (33.4 mm) | 0.957" | 0.179" |
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| Copper Type K | 1.125" (28.6 mm) | 0.995" | 0.065" |
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| Copper Type L | 1.125" (28.6 mm) | 1.025" | 0.050" |
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| Copper Type M | 1.125" (28.6 mm) | 1.055" | 0.035" |
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| PEX (Uponor AquaPEX) | 1.125" (28.6 mm) | 0.862" | n/a |
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| CTS CPVC (FlowGuard Gold) | 1.125" (28.6 mm) | n/a | 0.102" |
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PVC and steel follow iron pipe size, copper, PEX and CTS CPVC copper tube size. At 1" the iron pipe size is 0.19" wider than copper tube size. Schedule 80 and Type K keep the same outside as the thinner pipe and tube of their kind, with a smaller inside.
What fits a 1 inch pipe
- Copper, PEX and CTS CPVC: SharkBite sizes its 1" push-to-connect fittings 1" CTS, for pipe 1-1/8" across, and they take copper, CTS CPVC and PEX.
- PEX clamps and hangers: for its PEX, Uponor says to use copper tube size supports and clamps whenever possible.
- Threaded steel: 1" pipe thread is 1.315" across with 11.5 threads per inch. That’s the same count as garden hose thread, on a much wider thread. See pipe thread size.
- PVC to copper or PEX: the outsides differ, so the joint takes a transition fitting. See PVC to copper and PEX to PVC.
Measuring your pipe
Measure across the end at its widest point. 1" copper (1.125") is only 0.075" wider than 3/4" PVC (1.050"), so work out the kind of pipe first: what pipe do I have? For the coin check on smaller pipe, see how to tell pipe size.
Common questions
What is the inside diameter of 1 inch PEX?
Uponor AquaPEX is 0.862" inside and 1.125" outside. Other makers' PEX has the same outside, as PEX is copper tube size; check the maker's sheet for its inside.
What is the inside diameter of 1 inch Schedule 40 steel pipe?
1.049" in Wheatland Tube's table, with a 0.133" wall. Its 1" Schedule 80 is 0.957" inside with a 0.179" wall.
How thick is 1 inch copper pipe?
In the Copper Development Association's tables, Type K has a 0.065" wall (0.995" inside), Type L 0.050" (1.025") and Type M 0.035" (1.055").
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Where we get our information from
The sizes come from the pipe makers’ own tables (Charlotte Pipe, Wheatland Tube, Uponor) and the Copper Development Association’s tube tables; the thread from the National Bureau of Standards tables and the fitting size from SharkBite’s installation guide. Checked against published data from Uponor, SharkBite, National Bureau of Standards, Charlotte Pipe and Copper Development Association (plus 1 more).
See all 9 sources
- National Bureau of Standards, Handbook H28 (1957) Part II: Table VII.2 (American Standard taper pipe threads, NPT) and Tables X.1–X.3 (hose coupling threads, NH)
- Uponor, Plumbing Design Assistance Manual (PEX is copper tube size)
- SharkBite (Reliance Worldwide), SharkBite Installation Guide (2020): pipe insertion depth table, integral PEX stiffener
- SharkBite (Reliance Worldwide), SharkBite PEX Installation Guide (2021): fits copper, CTS CPVC and PEX in any combination
- Uponor, PEX Piping Systems Installation Guide, seventh edition (2025): ProPEX expansion fittings, pipe colors, copper and threaded adapters, no soldering within 18" of PEX
- Charlotte Pipe, Plastics Technical Manual (2026), product data: average outside diameter and minimum wall of PVC Schedule 40 and 80, PVC DWV, PVC and ABS foam core, 4" sewer and drain pipe, and CTS CPVC
- Copper Development Association, The Copper Tube Handbook (2026), Tables 14.2a-d: outside diameter, inside diameter and wall of Type K, L, M and DWV tube; outside diameter 1/8" over the standard size
- Uponor, Uponor AquaPEX white straight lengths submittal (2026): inner and outer diameter, 1/2" to 3"
- Wheatland Tube, Standard Pipe (SureThread and ERW) brochure: ASTM A53 Schedule 40 and 80 outside diameter, inside diameter and wall, black and galvanized, ASME B36.10M
General guidance from manufacturer and standards data. Parts vary by brand, so check the size printed on the package against what you measured. For gas lines or anything inside a wall, use a licensed plumber.