What size is my pipe, hose or fitting?
Pick where the part is and answer a question or two. You get its name and size, and what connects to it.
Where is the part?
Measure it
Use a tape or a caliper. Type a fraction, such as 11/16, or millimetres.
What are you measuring?
Measure across the outside of the tube or pipe. Many drip tubes and pipes also have the size printed along the side.
Threads per inch (if you can count them)
You most likely have
Enter the outside diameter, for example 0.70, 5/8 or 1 1/16 (inches), or 17.8 (mm).
How wide is the pipe?
Compare the pipe’s end with a coin.
Where are the threads?
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.
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.
What do you need to know?
What’s under the toilet?
Measure across the outside of the pipe from a basement or crawl space below.
How far is it from the wall to the bolt caps?
Measure from the finished wall, not the baseboard, to the center of a bolt cap at the base. With the toilet off, measure to the center of the drain.
Look under the spout, where it meets the wall. What’s there?
Use a flashlight. The screw sits in a small slot or hole on the underside.
What sticks out of the wall?
How wide is the old flapper?
Lay a tape across the rubber flapper at its widest part.
How wide is the hole it covers?
Turn the water off and flush to empty the tank, then measure across the opening at the bottom.
What’s printed on the tubing?
Look along the tubing for a number like .700 OD. Most makers repeat it every few feet.
How wide is it next to a dime?
Hold a dime against the cut end of the tubing.
What’s on the end of the spout?
Which coin is it closest to across?
Unscrew the aerator and hold coins against its end.
Start overWhat comes out of the wall?
Which kind of end?
You most likely have
Outdoor faucet or hose male end
Male hose thread, as on a spigot spout, a washing machine valve or the far end of a hose.
On the package: 3/4 in. male hose thread, MHT
Available on Amazon
Connect it to
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
Connect it to
Start overYou 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
Connect it to
Start overYou 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
Connect it to
Start overYou 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
Connect it to
Start overYou 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
Connect it to
Start overYou 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
Connect it to
Start overYou most likely have
A flange that fits over 3" pipe
3" PVC is 3.5" across. A 3" x 4" flange is cemented over it, and so is one sold as 3" hub.
On the package: 3 in. x 4 in. closet flange, or 3 in. hub
Available on Amazon
See also
Start overYou most likely have
A flange that fits inside 4" pipe, or over it
4" PVC is 4.5" across. A 3" x 4" flange goes inside it, and a 4" hub flange fits over it.
On the package: 3 in. x 4 in. (inside 4 in.) or 4 in. hub
Available on Amazon
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Start overYou most likely have
A cast iron repair flange
Repair flanges either slide over the cast iron pipe and seal with a gasket as their bolts tighten, or go inside it and seal as they’re turned or tightened.
On the package: Cast iron repair flange, over or inside the pipe
Available on Amazon
See also
Start overYou most likely have
A flange spacer kit
Spacers stack on the existing flange to bring it up to the finished floor, with longer closet bolts.
On the package: Closet flange spacer kit
Available on Amazon
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Start overYou most likely have
An offset flange
It moves the toilet’s connection up to 2" forward, back or sideways, and keeps the same opening inside.
On the package: Offset closet flange, 3 in. x 4 in.
Available on Amazon
See also
Start overYou most likely have
10" rough-in
The new toilet needs a 10" rough-in. Each toilet is made for at least its own rough-in, so a 12" model won’t fit.
On the package: 10 in. rough-in
Available on Amazon
See also
Start overYou most likely have
12" rough-in
The most common rough-in today.
On the package: 12 in. rough-in
Available on Amazon
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Start overYou most likely have
14" rough-in
Found mostly in older homes. A 14" toilet fits. A 12" one fits too but sits about 2" farther from the wall.
On the package: 14 in. rough-in
Available on Amazon
See also
Start overYou most likely have
Measure again
Rough-ins come out close to 10", 12" or 14". Check you went from the finished wall, not the baseboard, to the center of the bolt or drain.
See also
Start overYou most likely have
Slip-on spout, for 1/2" copper
A slip-on (slip-fit) spout slides over 1/2" copper pipe, held by the set screw underneath. Loosen that screw, then twist and pull the spout off.
On the package: Slip-on or slip-fit, 1/2 in. copper
Available on Amazon
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Start overYou most likely have
Threaded spout, for 1/2" pipe thread
It screws onto a pipe nipple with 1/2" male pipe thread. To take it off, turn the whole spout counterclockwise, with a strap wrench if it’s tight.
On the package: 1/2 in. IPS, also sold as 1/2 in. NPT
Available on Amazon
See also
Start overYou most likely have
A tub spout adapter
Many Delta spouts screw onto an adapter like this. The adapter is threaded, soldered or clamped with a set screw onto the pipe, and an O-ring on it seals inside the spout.
See also
Start overYou most likely have
2-inch flapper
The old flapper is about 3" across.
On the package: 2 in. flapper
Available on Amazon
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Start overYou most likely have
3-inch flapper
The old flapper is about 4" across.
On the package: 3 in. flapper
Available on Amazon
See also
Start overYou most likely have
A canister (tower) flush valve
It has no flapper. It takes a replacement seal.
On the package: Canister seal for your toilet’s model
See also
Start overYou most likely have
American Standard Champion 4 valve
A 4" opening takes a Champion 4 seal where other toilets use a flapper.
On the package: Champion 4 replacement seal
Available on Amazon
See also
Start overYou most likely have
.620" drip tubing
Sold as 1/2", .520" inside. DIG’s compression fittings for it have a green insert.
On the package: .620 OD x .520 ID
Available on Amazon
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Start overYou most likely have
.700" drip tubing
Sold as 1/2", .600" inside. DIG’s compression fittings for it have a black insert. Rain Bird calls it 700 series.
On the package: .700 OD
Available on Amazon
Connect it to
Start overYou most likely have
.710" drip tubing
Sold as 1/2", .620" inside. DIG’s compression fittings for it have a blue insert. Rain Bird calls it 710 series.
On the package: .710 OD
Available on Amazon
Connect it to
Start overYou most likely have
16–17 mm dripline
Rain Bird XF (0.634") and Netafim Techline CV (0.660") take their makers’ own fittings, not .700" or .710" compression.
On the package: 16 mm or 17 mm dripline
Available on Amazon
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Start overYou most likely have
.620" tubing or 16–17 mm dripline
All are narrower than a dime. A caliper tells them apart: .620", 0.634" (Rain Bird XF) or 0.660" (Netafim).
On the package: .620 OD, or 16 mm or 17 mm dripline
Available on Amazon
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Start overYou most likely have
.700" or .710" tubing
They’re only .010" apart, too close for a coin or a tape. Check the print, or use a universal fitting, which fits all three half-inch sizes.
On the package: .700 or .710 OD
Available on Amazon
Connect it to
Start overYou most likely have
A hidden (cache) aerator
A one-piece plastic aerator with male threads, screwed inside the spout. It comes out only with a key made for its size.
On the package: Key and replacement for your faucet’s cache aerator
Available on Amazon
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Start overYou most likely have
Kitchen or bathroom faucet
The spout where the aerator (the little screen) screws on.
On the package: 15/16"-27 male or 55/64"-27 female aerator thread
Available on Amazon
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Start overYou most likely have
Standard aerator
Quarter-size. Threads outside (male): 15/16"-27. Threads inside (female): 55/64"-27.
On the package: Standard, 15/16 in.-27 male or 55/64 in.-27 female
Available on Amazon
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Start overYou most likely have
Junior aerator
Nickel-size. Threads outside (male): 13/16"-27. Threads inside (female): 3/4"-27.
On the package: Junior, 13/16 in.-27 male or 3/4 in.-27 female
Available on Amazon
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Start overYou most likely have
Tiny Junior aerator
Penny-size, with metric threads. Threads outside (male): M20x1. Threads inside (female): M19x1 in Neoperl’s sizes, M18.5x1 on Danco’s chart.
On the package: Tiny Junior, M20x1 male or M19x1 female
Available on Amazon
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Start overYou most likely have
Tom Thumb aerator
Dime-size, with metric threads. Threads outside (male): M18x1. Threads inside (female): M16x1.
On the package: Tom Thumb, M18x1 male or M16x1 female
Available on Amazon
See also
Start overYou most likely have
Shutoff valve under a sink or toilet
The small valve on the wall. Its outlet is usually 3/8" compression.
On the package: 3/8 in. compression outlet
Available on Amazon
Connect it to
Start overYou most likely have
1/2" copper pipe out of the wall
No valve yet. 5/8" across.
On the package: 1/2 in. nominal copper, 5/8 in. O.D.
Available on Amazon
Connect it to
Start overYou most likely have
1/2" PEX tubing out of the wall
No valve yet. Plastic, 5/8" across.
On the package: 1/2 in. PEX
Available on Amazon
Connect it to
Start overYou most likely have
Garden hose (female end)
The end that screws onto a faucet, with threads inside and a rubber washer.
On the package: 3/4 in. female hose thread, FHT
Available on Amazon
Connect it to
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How to tell sizes apart
- 1/2" or 3/4" pipe: 1/2" pipe, pipe thread and PVC are 0.84" across, about the width of a nickel (0.835"). 3/4" is 1.05" across, a little wider than a quarter (0.955").
- Hose thread or pipe thread: at 3/4" they’re almost the same width, so count the threads over one inch. Hose thread has 11.5, pipe thread has 14.
- Copper or PEX: at 1/2" both are 5/8" across. Copper is metal; PEX is plastic tubing.
- Where it is tells you most: an outdoor faucet’s spout takes a garden hose, and the shutoff valve under a sink or toilet usually has a 3/8" compression outlet.
How to measure
- Threads: measure across the tops of the threads on a male part (threads on the outside). For a female part, measure the male part that screws into it.
- Tubing and pipe: measure across the outside. Close the caliper gently: soft drip tubing squashes if you press hard.
- Use a caliper if you can. The common drip sizes differ by as little as .010", and 3/4" hose and pipe thread by 1/80". A tape gets you close; Measure it then shows every size that close and how to tell them apart.
- Count threads by laying a ruler along the thread and counting the peaks in one inch. 11½ is hose thread (or 1" pipe); 14 is 1/2" or 3/4" pipe.
Common sizes
Outside diameters: threads, pipe and tubing
| What it is | Across (OD) | Threads per inch |
|---|---|---|
| 1/4" pipe thread (NPT) | .540" | 18 |
| 3/8" pipe thread (NPT) | .675" | 18 |
| 1/2" pipe thread (NPT) | .840" | 14 |
| Faucet spout with outside threads (55/64"-27) | .859" | 27 |
| Aerator with outside threads (15/16"-27) | .938" | 27 |
| 3/4" pipe thread (NPT) | 1.050" | 14 |
| Garden hose thread (GHT) | 1.0625" | 11½ |
| 1" pipe thread (NPT) | 1.315" | 11½ |
| .220" drip tubing (sold as 1/4") | .220" | smooth |
| .245" drip tubing (sold as 1/4") | .245" | smooth |
| .250" drip tubing (sold as 1/4") | .250" | smooth |
| 1/4" ice maker tube | .250" | smooth |
| 3/8" supply tube | .375" | smooth |
| 1/2" OD supply tube | .500" | smooth |
| .620" drip tubing (sold as 1/2") | .620" | smooth |
| 1/2" copper or PEX | .625" | smooth |
| .634" drip tubing (sold as 1/2") | .634" | smooth |
| .660" drip tubing (sold as 1/2") | .660" | smooth |
| .700" drip tubing (sold as 1/2") | .700" | smooth |
| .705" drip tubing (sold as 1/2") | .705" | smooth |
| .710" drip tubing (sold as 1/2") | .710" | smooth |
| 1/2" PVC or steel pipe | .840" | smooth |
| 3/4" copper or PEX | .875" | smooth |
| 3/4" PVC or steel pipe | 1.050" | smooth |
| 1" PVC or steel pipe | 1.315" | smooth |
Threads: across the tops of a male thread. Pipe-thread sizes are the pipe’s outside diameter; a caliper on the thread reads a little less.
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Common questions
How do I tell garden hose thread from pipe thread?
Count the threads over one inch. Garden hose thread has 11.5; 1/2" and 3/4" pipe thread have 14. Measuring alone can't separate 3/4" hose thread (1.0625" across) from 3/4" pipe thread (1.050").
Why does my 1/2 inch pipe measure 0.84 inches?
Pipe is named by a nominal size, not its outside diameter. 1/2" iron pipe size (steel, brass, Schedule 40 and 80 PVC, and 1/2" pipe thread) is 0.840" across; 3/4" is 1.050".
What size is my 1/2 inch copper or PEX?
1/2" copper and PEX are 0.625" (5/8") across. Copper tube size is the nominal size plus 1/8".
How do I know which 1/2 inch drip tubing I have?
Look for the size printed on the tubing every few feet, or measure the outside: about .620", .700" or .710" are the common sizes. Use compression fittings for that exact size, or universal fittings.
Where we get our information from
The sizes come from published thread and pipe standards and the makers’ own spec sheets, and the coin sizes from the US Mint. Checked against published data from Rain Bird, Fluidmaster, DIG Corp., BrassCraft and Kohler (plus 18 more).
See all 46 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)
- Dixon Valve, Technical Information: Identifying Threads and Thread Dimensions (2009 catalog)
- 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)
- BrassCraft, angle stop product pages (compression, FIP, sweat, PEX and push-connect inlets; 3/8", 7/16", 1/2" and 1/4" O.D. outlets; 1/2" nominal = 5/8" O.D.)
- Fluidmaster, faucet and toilet connector catalogs and Click Seal pages (FM91429, FM91233)
- BrassCraft, dishwasher (B1-DW, B1-60DW1) and ice maker (B0-IM) connectors
- BrassCraft, installation instructions for connectors (425.10, 425.07, B0120IMB) and water supply stops (425.04)
- DIG Corp., “Tubing & Fittings for Drip Irrigation”
- DIG Corp., 1/2" .700 OD poly drip tubing product page
- Rain Bird, XFD/XFDe dripline specifications
- Netafim, Techline CV specification sheet
- Rain Bird, UltraXP poly tubing and XQ 1/4" distribution tubing specifications
- Rain Bird, Easy Fit compression fitting system
- Netafim, 17 mm dripline fittings
- Rain Bird, XBS tubing chart (discontinued line)
- DIG Corp., 1/4" poly and vinyl micro tubing product pages
- Rain Bird, 1/2" barbed drip fittings (OD 0.63", ID 0.54")
- JM Eagle, PVC Schedule 40/80 submittal (ASTM D1785 outside diameters)
- Swagelok, Thread Sealants catalog (MS-14-01): PTFE tape, how to apply
- Fluidmaster, “Determining Whether You Have a 2" or 3" Flush Valve and Flapper”
- Fluidmaster, flapper product pages and FAQs (502, 513A, 5403)
- Fluidmaster, “Choosing the Right Flapper for Your Toilet”
- Korky, “What Size Flapper Do I Need?” and Fit-All flapper page
- Kohler, Toilet Service Parts catalog (2015)
- American Standard, Champion 4 universal flush valve kit
- Korky, Champion 4 replacement seal
- Neoperl, aerators with housings, aftermarket and manufacturer pages (thread sizes by insert size, including Tiny Junior and metric Standard) and “Replacing a faucet aerator”
- Danco, Multi-Fit Aerator Key instructions (10909): coin sizes and male/female aerators
- Delta, FAQ: connecting a portable dishwasher or water filter to a kitchen faucet (cache aerators, RP51505)
- Oatey, Solvent Welding Instruction Guide
- Flexzilla, “What Causes a Leaky Garden Hose”
- DIG Corp., compression fittings by tubing OD (.450 to .710)
- United States Mint, Coin Specifications (dime 0.705", nickel 0.835", quarter 0.955" diameter)
- Charlotte Pipe, Submittal Package, PVC Schedule 40 DWV System (2026): average outside diameters
- Moen, Tub Spout Gate Assembly instructions (INS708): slip fit spouts have a set screw underneath, IPS spouts don't
- Moen, one-handle tub/shower valve trim installation instructions (INS2153E): IPS spouts on 1/2" male pipe thread, slip fit on 1/2" copper only, pipe lengths
- Kohler, Bath Spouts installation guide (K-15135 to K-15138, 1011610-2-D): 1/2" NPT nipple, slip-fit copper tube length, setscrew
- Delta, Tub Spout Installation (107700 Rev. M): threaded, slip-on and adapter spouts, pipe lengths by model, no PEX drop
- Neoperl, Aerators with integrated thread: one-piece male-thread aerators, available thread sizes, a key for each size
- Kohler, Corbelle K-33814 and K-5381 specification sheets: standard 12" rough-in, 10" and 14" rough-in kits
- American Standard, Cadet Pro 10" rough-in toilet specification sheet (215AB.104): minimum 10" from finished wall to outlet center; Cadet Pro installation instructions (7301878-100): turn off water, cover an open flange
- TOTO, Toilet Rough-ins and the Unifit Rough-in, and the TOTO toilet buyer guide: how to measure, 10", 12" and 14"
- Oatey, Toilet Flanges page and FAQs: spacer kits, cast iron repair flanges, setting the flange on the finished floor
- Oatey, Should You Use an Offset Toilet Flange?: up to 2" offset, 3" x 4" over 3" or inside 4" pipe
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.