Pipe Measurements: Explained
Actual Outside Diameter (OD)
This is the measurement of the pipe, from the top to the bottom or the left to the right, from the outside edges of the pipe.
This measurement does not equal the PVC pipe size.
Average Inside Diameter (ID)
This is the measurement of the pipe, from the top to the bottom or the left to the right, from the inside hole (bore) of the pipe.
This is the measurement that is used to determine the PVC pipe size
Wall Thickness (Wall)
This is the measurement of the thickness of the PVC pipe wall from the outside to the inside.
The wall thickness is the measurement that changes between the different Schedules of PVC pipe.
PVC Schedule 40 Sizes Table
Schedule 40 PVC pipe is compatible with all FORMUFIT external-fit and internal-fit products. If you prefer to measure the outside diameter (OD) of your pipe to determine the PVC pipe size, use the table below:
- Take your OD measurement and look in the Decimal OD, Fraction OD or Metric OD (depending on your measurement method) columns of the table below.
- Once the pipe OD is determined, trace your OD measurement to the Pipe Size column in the chart below; this will be the Nominal Pipe Size (NPS), or the size of fittings or pipe you want to order.
PVC Schedule 80 Sizes Table
Schedule 80 PVC pipe is only compatible with FORMUFIT external-fit products. FORMUFIT internal-fit products, such as Internal Dome Caps, Adjustable Elbows, Internal Couplings and other products that fit inside of the PVC pipe will not work with SCH 80 PVC due to the smaller internal diameter.
If you prefer to measure the outside diameter (OD) of your pipe to determine the PVC pipe size, use the table below:
- Take your OD measurement and look in the Decimal OD, Fraction OD or Metric OD (depending on your measurement method) columns of the table below.
- Once the pipe OD is determined, trace your OD measurement to the Pipe Size column in the chart below; this will be the Nominal Pipe Size (NPS), or the size of fittings or pipe you want to order.
PVC Thinwall Sizes Table
Thinwall PVC pipe is only compatible with FORMUFIT external-fit products. FORMUFIT internal-fit products, such as Internal Dome Caps, Adjustable Elbows, Internal Couplings and other products that fit inside of the PVC pipe will not work with Thinwall PVC due to the larger inner diameter.
Please note that not all PVC sizes are available in Thinwall PVC pipe and that the wall thicknesses and internal diameters are considered proprietary and not industry standard.
If you prefer to measure the outside diameter (OD) of your pipe to determine the PVC pipe size, use the table below:
Take your OD measurement and look in the Decimal OD, Fraction OD or Metric OD (depending on your measurement method) columns of the table below.
Once the pipe OD is determined, trace your OD measurement to the Pipe Size column in the chart below; this will be the Nominal Pipe Size (NPS), or the size of fittings or pipe you want to order.
Other Dimensions and Ratings
Please note that FORMUFIT does not provide pressure rating or temperature ratings for PVC pipe and fittings as our products are designed for structural use and are not ideal for plumbing applications. While our products do carry the same ratings as standard Schedule 40 and PVC plumbing pipe and fittings, they have not been tested with the National Sanitary Foundation (NSF) for residential or commercial plumbing applications. They are approved for aquarium, irrigation and hydroponics use
CPVC Pipe
CPVC pipe, also known as Copper Tube Size (CTS) plastic pipe uses a different measurement system and is not compatible with FORMUFIT PVC products. Please see our CPVC Identification Page for more information.
Acrylic Pipe
Acrylic pipe uses a different measurement system and is not compatible with FORMUFIT PVC products.
EMT Conduit
EMT Conduit or Electrical metallic tubing pipe uses a different measurement system and is not compatible with FORMUFIT PVC products.