Pipe Size Reference Chart: Nominal and Outer Diameters

Pipe nominal diameter and actual outer diameter often do not match in piping standards.

For that reason, we recommend checking the actual outer diameter rather than the nominal diameter. In this article, we’ve compiled the recommended compatible sizes for our products based on the nominal diameters and outer diameters of PVC pipe, steel pipe, and copper pipe.

What you’ll learn in this article

• Why nominal diameter and actual outer diameter differ
• Nominal diameter, outer diameter, and recommended compatible sizes by pipe type
• Points to note when checking sizes

The difference between "nominal diameter" and "outer diameter"

Nominal diameter is basically a standardized piping term based on "inner diameter", so, as shown in the table below, the outer diameter of the pipe often differs.

Pipe type	Nominal diameter	Inner diameter	Outer diameter
PVC pipe	VP20	20mm	26mm
Steel pipe	20A	around 21.6mm	27.2mm

 

Therefore, we recommend choosing the appropriate compatible size based on the actual outer diameter rather than the nominal diameter. Below, along with compatibility tables for nominal diameter and outer diameter by pipe type, we summarize the recommended compatible sizes for our products.

PVC pipe (VP) nominal diameter / outer diameter compatibility table

Nominal diameter	Outer diameter	Compatible products
		Saddle	Clamp
VP13	18mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP16	22mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP20	26mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP25	32mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP30	38mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP40	48mm	Standard type Anti-vibration type	Standard type Anti-vibration type
VP50	60mm	Standard type	Standard type Anti-vibration type
VP65	76mm	-	Standard type Anti-vibration type
VP75	89mm	-	Standard type
VP100	114mm	-	Standard type

Steel pipe (GP) nominal diameter / outer diameter compatibility table

Nominal diameter	Outer diameter	Compatible products
		Saddle	Clamp
10A	17.3mm	Standard type Anti-vibration type	Anti-vibration type
15A	21.7mm	Standard type Anti-vibration type	Standard type Anti-vibration type
20A	27.2mm	Standard type Anti-vibration type	Standard type Anti-vibration type
25A	34.0mm	Standard type Anti-vibration type	Standard type Anti-vibration type
32A	42.7mm	Standard type Anti-vibration type	Standard type Anti-vibration type
40A	48.6mm	Standard type Anti-vibration type	Standard type Anti-vibration type
50A	60.5mm	Standard type	Standard type Anti-vibration type
65A	76.3mm	-	Standard type Anti-vibration type
80A	89.1mm	-	Standard type
100A	114.3mm	-	Standard type

* Some sizes are approximate, but installation is still possible without any issues.

Copper pipe (CU) nominal diameter / outer diameter compatibility table

Nominal diameter	Outer diameter	Compatible products
		Saddle	Clamp
CU13	15.88mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU16	19.05mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU20	22.23mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU25	28.58mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU32	34.92mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU40	41.28mm	Standard type Anti-vibration type	Standard type Anti-vibration type
CU50	53.98mm	Anti-vibration type	Standard type Anti-vibration type
CU65	66.68mm	-	Standard type
CU80	79.38mm	-	Standard type

* Please note that nominal diameter and outer diameter may differ depending on the application, such as copper pipe for building plumbing or copper refrigerant pipe (including insulation).

* Some sizes are approximate, but installation is still possible without any issues.

Notes when checking pipe size

In some cases, actual measurement is necessary

Depending on the pipe type and usage conditions, the actual dimensions may vary slightly. If you are unsure, we recommend measuring directly with calipers or a measuring tape. For the correct measuring method, please see How to Measure Pipe Outer Diameter | How to Check Size with Calipers and a Measuring Tape.

Related articles

• How to Measure Pipe Outer Diameter | How to Check Size with Calipers and a Measuring Tape
• What is pipe nominal diameter? A size-by-size explanation of how it differs from the outer diameter
  
• Plastic saddle band size selection guide | Why you should choose based on outer diameter, not nominal diameter
• Plastic pipe clamp size selection guide | How to choose based on the pipe’s outer diameter