PVC Pipe Sizes: A Guide to Understanding OD Sizes
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Time to read 3 min
There are many different sizes of PVC pipe. Some are tiny, at 1/2", but others are huge at 12". The problem is that what the industry calls a 1" pipe is not actually 1" in diameter. Because of this confusing issue, many of our customers ask us, "What is the outside diameter of PVC pipe?" If you have the same question, it can be answered by the chart below. Keep reading to learn why the outer diameter, or "OD" of PVC pipe is not the same as what the name says.
What is the OD of PVC Pipe?
The outer diameter of PVC pipe is actually slightly larger than what its name says. This is because PVC pipe and fittings use a nominal system. That means that compatible parts are given the same name, so all 1" pipe will fit in 1" fittings and so on. The measurements in pipe names are the PVC nominal pipe sizes, but not how necessarily how far they measure across. This is a confusing concept, but the point of this nominal system is to make selecting the right parts easier.
PVC Pipe OD Chart vs. PVCP Pipe Size
The PVC pipe OD chart below shows the nominal size of the PVC pipe on the left along with the actual OD on the right. As mentioned before, the OD for schedule 40 and schedule 80 PVC pipe are always the same.
How to Measure the Outside Diameter of PVC Pipe
- Look at the end of a piece of PVC pipe.
- Find the widest point across the opening.
- Measure from the outside edge of the pipe to the opposite outside edge.
- This measurement is the outside diameter or "OD" of the pipe.
OD: Schedule 40 vs. Schedule 80
For regular schedule 40 PVC pipe, the title 1", for instance, means that the inner diameter (ID) is 1". The pipe walls themselves have a thickness, though. The OD of 1" PVC pipe is 1.315". Schedule 80 PVC pipe has thicker walls than schedule 40, but still has the same OD. This means that the ID of 1" schedule 80 PVC pipe is actually slightly less than 1". While ID of pipe may vary by schedule, the ID of fittings is always the same as the OD of the pipe it is meant to work with. Regardless of schedule, a 1" PVC pipe will fit into a 1" fitting. The outside diameter of PVC pipe fittings is unimportant, as you will probably never be putting a fitting inside a bigger fitting.
Wall Thickness
As PVC pipe increases in diameter, the walls must also be thicker. If the walls were too thin, the pipe would lack structural integrity. To find PVC pipe OD sizes, you cannot simply add a certain amount to the size on the label. The OD for 1/2" PVC pipe is 0.840" and the OD for 3" PVC pipe is 3.500". If the nominal size is the ID, then that means 1/2" PVC pipe walls are .170" thick and 3" PVC pipe walls are 0.250" thick. The wall thickness continues increasing as the pipe gets larger.
Is the nominal PVC pipe size the same as the outside diameter?
No. The nominal size (e.g., 1-inch pipe) is a designation used for identification and does not represent the actual physical measurement. The outside diameter (OD) is always larger than the nominal size to ensure the pipe fits correctly into standard fittings.
Does Schedule 40 and Schedule 80 PVC have the same OD?
Yes. Both Schedule 40 and Schedule 80 PVC pipes have the exact same outside diameter. This allows them to use the same fittings. The difference lies in the wall thickness; Schedule 80 has a thicker wall, which results in a smaller inside diameter (ID).
How do I accurately measure the size of my PVC pipe?
To find the nominal size, measure the outside diameter with a caliper or tape measure and compare it to a PVC size chart. For example, if your pipe measures 1.315 inches on the outside, it is actually a 1-inch nominal PVC pipe.
Why is PVC pipe measured by the outside diameter?
PVC is measured by its outside diameter to ensure compatibility with fittings. Because fittings slip over the outside of the pipe, the OD must remain constant across different "schedules" (thicknesses) so that a 2-inch fitting always fits a 2-inch pipe.
Mark Ligon
Mark Ligon is the marketing manager at PVC Fittings Online, a supplier of commercial PVC and CPVC pipe, fittings and valves. Ligon enjoys educating businesses on the parts of piping systems so managers can make informed decisions. He can be reached at webmaster@commercial-industrial-supply.com.
