Pipe Size Chart: PVC, Copper, PEX and Steel Pipe Dimensions

How pipe sizes work

Three sizing systems cover nearly every pipe in a building. Knowing which one a pipe uses tells you what fits it.

• Nominal pipe size (NPS), also called iron pipe size (IPS): steel, galvanized, black iron, brass and PVC/ABS pipe. The outside diameter is fixed for each size, and the schedule sets the wall thickness. Above 12 in, the nominal size equals the OD; below it, the name is only loosely related to any real dimension.
• Copper tube size (CTS): copper water tube, PEX and CPVC water pipe. The outside diameter is always 1/8 in larger than the nominal size.
• Metric (DN and OD in mm): used outside North America. DN (diamètre nominal) matches NPS steel pipe; metric plastic pipe is named by its actual OD in mm.

PVC and steel pipe sizes: Schedule 40 and 80

Schedule 40 and Schedule 80 share the same outside diameter, so they take the same fittings. Schedule 80 has a thicker wall, a smaller bore and a higher pressure rating.

To identify a pipe, measure its outside diameter, not the inside: a pipe with a 1.05 in OD is 3/4 in, and one at 1.9 in is 1 1/2 in, whatever its wall thickness. A quick check is circumference: wrap a tape around it and divide by 3.1416.

PVC pressure ratings

These ratings are for the pipe at 73°F. They fall quickly with heat (to roughly a fifth at 140°F, PVC's upper limit), fittings are rated lower than pipe, and threading Schedule 80 halves its rating. PVC is for cold water, irrigation and drains; hot water needs CPVC, PEX or copper.

Copper pipe sizes: Type K, L and M

All three types have the same outside diameter for a given size and fit the same fittings. Only the wall thickness changes. Type L (blue print) is the usual choice for water lines inside a house, Type M (red) is thinner and allowed by many codes for interior water lines, and Type K (green) is the thick-walled tube for underground service lines.

Refrigeration and air-conditioning (ACR) copper is named by its actual OD instead, so 5/8 in ACR tube is the same tube as 1/2 in water tube. Metric copper in Europe is 15, 22 and 28 mm OD, close to but not the same as US 15.9, 22.2 and 28.6 mm, so use adapters rather than forcing fittings.

PEX pipe sizes

PEX tubing follows copper tube size with a standard dimension ratio of 9, meaning the wall is one-ninth of the OD. That thicker wall makes the bore smaller than copper of the same size.

A 1/2 in PEX line has about 79% of the flow area of 1/2 in Type L copper (0.485² ÷ 0.545²). On long runs or for fixtures that need high flow, such as a tub filler, step up to 3/4 in. Bore holes for 1/2 in PEX with a 3/4 or 7/8 in bit; the drill bit guide lists sizes.

Pipe sizes for household fixtures

Supply sizes come from IPC Table 604.5 and trap sizes from IPC Table 709.1; many jurisdictions use the Uniform Plumbing Code instead, with similar numbers. Fixture dimensions are covered in our shower, bathtub, kitchen sink and washing machine guides.

Pipe thread sizes (NPT)

Threaded steel, brass and PVC fittings use National Pipe Taper (NPT) threads, sized by nominal pipe size. The thread is cut on the pipe's outside diameter, so a 1/2 in NPT male thread is about 0.84 in across.

NPT is not the same as British BSP thread (used in the UK, Europe and Australia) or garden hose thread (GHT, 3/4 in with 11 1/2 threads per inch). A 1/2 in BSP fitting has 14 threads per inch but a different thread angle, so it may start on NPT and then leak. Garden hose fittings are covered in the garden hose size guide.

Frequently asked questions