The size of your PVC pipe is identified using the inside diameter measurement of the pipe - this measurement is known as 'Nominal', which means a referenced name. One of the issues that is commonly encountered when trying to measure pipe size is that the outside diameter of the pipe is often measured and incorrectly provided, which actually gives you a completely different (and larger) PVC pipe dimension then what you may actually require.

If you are going to measure the outside diameter of the pipe, do the following:

1. Take your outside diameter measurement, and then refer to the tables below for the Actual Outside Diameter
2. Once you find the actual outside diameter of the pipe in the chart, then look at the Pipe Size beside it - this will be the nominal pipe size, and tell you the size of fittings you want to be ordering

PVC Schedule 40 Sizing Table

Schedule 40 PVC pipe is compatible with all external-fit and internal-fit fittings.

PVC Schedule 80 Sizes Table

Schedule 80 PVC pipe is only compatible with external-fit fittings. Internal-fit fittings, such as Internal Dome Caps, Adjustable Elbows, Internal Couplings and other fittings that fit inside of the PVC pipe will not work with SCH 80 PVC due to the smaller internal diameter.

PVC Thinwall Sizes Table

Thinwall PVC pipe is only compatible with external-fit fittings. Internal-fit fittings, such as Internal Dome Caps, Adjustable Elbows, Internal Couplings and other fittings that fit inside of the PVC pipe will not work with Thinwall PVC due to the larger inner diameter.

Not all sizes are available in Thinwall PVC pipe.

CPVC Pipe

CPVC pipe, also known as Copper Tube Size (or CTS) plastic pipe uses a different system for measurement, and is not compatible with standard PVC fittings.

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