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How to tell if a pipe is 1/2" or 3/4"

Measure across the outside of the pipe, or hold a coin against the end. For copper and PEX, 1/2" is 5/8" across and 3/4" is 7/8", and for PVC and threaded pipe, 1/2" is 0.84" and 3/4" is 1.05".

What kind of pipe is it?

CopperCopper-colored metal, no threadsPEXFlexible plastic tubingPVCRigid white plastic pipeThreaded pipe or fittingMetal or plastic, with threadsNot sureTell the kinds of pipe apart

Where are the threads?

On the outsideA pipe end or fitting that screws into somethingOn the insideA fitting that something screws into
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What size is the fitting?

Look for a size printed on it. If there isn’t one, hold a coin against the pipe that screws into it.

1/2"Takes a pipe about as wide as a nickel3/4"Takes a pipe a little wider than a quarterNot sureMeasure it instead
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How wide is it across the threads?

Hold a coin against the end. Garden hose thread is about as wide as 3/4" pipe thread, so if this is on a hose or an outdoor faucet, go back and pick that.

About as wide as a nickel1/2" pipe: 0.84" acrossA little wider than a quarter3/4" pipe: 1.05" acrossNeitherMeasure it instead
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How wide is the pipe?

Compare the pipe’s end with a coin.

About as wide as a nickel1/2" PVC: 0.84" acrossA little wider than a quarter3/4" PVC: 1.05" acrossNeitherMeasure it instead
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How wide is the PEX?

Set a dime and a nickel next to it.

Narrower than a dime1/2" PEX: 5/8" (0.625") acrossA little wider than a nickel3/4" PEX: 7/8" (0.875") acrossNeitherMeasure it instead
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How wide is the copper pipe?

Compare its end with a dime and a nickel.

Narrower than a dime1/2" copper: 5/8" (0.625") acrossA little wider than a nickel3/4" copper: 7/8" (0.875") acrossNeitherMeasure it instead
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You most likely have

1/2" fitting, threads inside

Female pipe thread (FIP) that takes a 1/2" pipe thread, 0.84" across.

On the package: 1/2 in. FIP, also sold as FPT or FNPT

Available on Amazon

PTFE thread seal tape
  • Tape goes on the male thread you screw into it, never inside the fitting.
  • A garden hose’s male end won’t screw in. Hose thread is about 1-1/16" across, far wider than 1/2" pipe.

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

3/4" fitting, threads inside

Female pipe thread (FIP) that takes a 3/4" pipe thread, 1.05" across.

On the package: 3/4 in. FIP, also sold as FPT or FNPT

Available on Amazon

PTFE thread seal tape
  • Wrap tape on the male thread that goes in, not on this fitting’s inside threads.
  • A hose’s male end looks close but won’t thread in. It has 11.5 threads per inch against pipe thread’s 14.

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

1/2" pipe, threads on the outside

Male pipe thread (MIP), 0.84" across.

On the package: 1/2 in. MIP, also sold as MPT or MNPT

Available on Amazon

PTFE thread seal tape
  • Pipe thread tapers and seals on the threads, so wrap them with thread tape or use pipe sealant.
  • It screws into a 1/2" female pipe thread (FIP) fitting.

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

3/4" pipe, threads on the outside

Male pipe thread (MIP), 1.05" across.

On the package: 3/4 in. MIP, also sold as MPT or MNPT

Available on Amazon

PTFE thread seal tape
  • Like all tapered pipe thread, it needs tape or sealant on these threads to seal.
  • 3/4" hose thread is nearly as wide, so count the threads. Pipe thread has 14 per inch, and hose thread has 11.5.

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

1/2" PVC pipe, plain end

White plastic pipe with no threads, 0.84" across.

On the package: 1/2 in. PVC

Available on Amazon

PVC primer and cement
  • Slip fittings for it are glued on with PVC primer and cement. Nothing screws onto a plain end.
  • 1/2" copper and PEX fittings won’t fit. Copper tube size is 5/8" across, narrower than this pipe’s 0.84".

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

3/4" PVC pipe, plain end

White plastic pipe with no threads, 1.05" across.

On the package: 3/4 in. PVC

Available on Amazon

PVC primer and cement
  • A 3/4" slip fitting is glued over the end with primer and cement.
  • It’s wider than 3/4" copper or PEX (7/8" across), so their fittings don’t fit it.

Connect it to

Garden hose (female end)Outdoor faucet or hose male end
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You most likely have

1/2" PEX tubing

PEX is made to copper tube size, so 1/2" PEX is 5/8" across.

On the package: 1/2 in. PEX

Available on Amazon

1/2" push-to-connect fittings
  • 1/2" push-to-connect fittings take it, the same ones that fit 1/2" copper.
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You most likely have

3/4" PEX tubing

PEX is made to copper tube size, so 3/4" PEX is 7/8" across.

On the package: 3/4 in. PEX

Available on Amazon

3/4" push-to-connect fittings
  • 3/4" push-to-connect fittings take it, the same ones that fit 3/4" copper.
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You most likely have

1/2" copper pipe

Copper tube size: 5/8" across, the nominal size plus 1/8".

On the package: 1/2 in. copper, 5/8 in. O.D.

Available on Amazon

1/2" push-to-connect fittings
  • A 1/2" push-to-connect fitting takes it. Cut the end square and deburr it first.
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You most likely have

3/4" copper pipe

Copper tube size: 7/8" across, the nominal size plus 1/8".

On the package: 3/4 in. copper, 7/8 in. O.D.

Available on Amazon

3/4" push-to-connect fittings
  • 3/4" push-to-connect fittings fit it. Mark the insertion depth from the fitting’s instructions.
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Why the name isn’t the measurement

Pipe is sold by a nominal size, which isn’t its width. Copper and PEX are made to copper tube size, where the outside is the nominal size plus 1/8". PVC and threaded steel or brass pipe are made to iron pipe size, which runs wider still.

Measuring with a tape

Hold the tape across the end of the pipe and read it at the widest point. Within one kind of pipe the sizes are far enough apart for a tape. Across kinds they aren’t: 3/4" copper (0.875") and 1/2" PVC (0.84") are only about 1/32" apart. Work out the kind of pipe first.

Not a pipe, or not sure what it is?

Identify any part

Common questions

Is 1/2 inch pipe really 1/2 inch across?

No. 1/2" copper and PEX measure 5/8" across the outside, and 1/2" PVC and threaded pipe measure 0.84". The 1/2" is the size's name.

How do I tell copper from PEX?

Copper is rigid metal; PEX is flexible plastic tubing. Both are made to copper tube size, so a 1/2" copper pipe and a 1/2" PEX tube are the same width.

Keep going

Identify itany partShutoff valve for copper pipeShutoff valve for PEXSharkBite fittingsGarden hose to PVCPipe thread size

Where we get our information from

The sizes on this page come from published standards and the makers’ own documents. Checked against published data from Swagelok, SharkBite, National Bureau of Standards, Copper Development Association and Uponor (plus 3 more).

See all 10 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)
  • Swagelok, Thread and End Connection Identification Guide (MS-13-77)
  • Copper Development Association, Copper Tube Handbook (ASTM B88 tube dimensions)
  • Uponor, Plumbing Design Assistance Manual (PEX is copper tube size)
  • JM Eagle, PVC Schedule 40/80 submittal (ASTM D1785 outside diameters)
  • Swagelok, Thread Sealants catalog (MS-14-01): PTFE tape, how to apply
  • Oatey, Solvent Welding Instruction Guide
  • 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
  • United States Mint, Coin Specifications (dime 0.705", nickel 0.835", quarter 0.955" diameter)

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.