Polyethylene Pipe Sizes in mm and Inches: Wall Thickness and Inside Diameter Chart

The size of a polyethylene pipe is its outside diameter in millimetres; ISO 4427, the basis for water supply pipes, defines pipe size by nominal outside diameter. So a “110 pipe” has an outside diameter of 110 mm, not an inside diameter of 110 mm, and that number stays the same across every pressure class of the size.

Even so, many buyers in Iran still name pipe in inches, calling a 63 mm pipe “2 inch” and a 110 mm pipe “4 inch”. These names are a convention, not an exact unit conversion, so always write the outside diameter in millimetres and the pressure class when you order, and if you only know the inch name, also say what the pipe is for.

The table below lists 22 common polyethylene pipe sizes from 20 to 630 mm with the common market inch name next to the wall thickness at three widely used pressure classes. The walls are for PE100 pipe at design coefficient 1.25: 6 bar is SDR 26, 10 bar is SDR 17 and 16 bar is SDR 11.

The last two columns give the inside diameter and the weight per metre at 10 bar; the inside diameter is the outside diameter minus twice the wall, and weights up to 560 mm come from the company’s approved weight table. The inch names were compared across three public Iranian market sources, and only sizes on which they agree are listed.

• PE100 water pressure pipe
• PE water and irrigation pipes
• PE pipe weight table

In market usage a 20 mm pipe is called “1/2 inch”, 25 mm “3/4 inch”, 32 mm “1 inch”, 63 mm “2 inch”, 90 mm “3 inch”, 110 mm “4 inch”, 160 mm “6 inch”, 200 mm “8 inch” and 315 mm “12 inch”. If you have heard a size in inches, this list helps you find its millimetre size.

Note that one inch is 25.4 mm, so “2 inch” is really 50.8 mm and not the same as a 63 mm outside diameter. The inch name is only a convention. Each size page on this site shows the wall thickness, inside diameter and weight of that size in every pressure class we publish.

• 32 mm (1 inch) HDPE pipe
• 63 mm (2 inch) HDPE pipe
• 90 mm (3 inch) HDPE pipe
• 110 mm (4 inch) HDPE pipe
• 160 mm (6 inch) HDPE pipe
• 200 mm (8 inch) HDPE pipe

The wall thickness of a polyethylene pipe follows from its SDR, the ratio of outside diameter to wall thickness: the smaller the SDR, the thicker the wall and the higher the allowed pressure. For PE100 at design coefficient 1.25, the 6 bar class is SDR 26, the 10 bar class SDR 17 and the 16 bar class SDR 11.

For example, a 110 mm PE100 pipe has a 4.3 mm wall at 6 bar, 6.5 mm at 10 bar and 10 mm at 16 bar. PE80 needs a thicker wall for the same pressure: a 110 mm PE80 pipe at 10 bar is SDR 13.6, with a 8.1 mm wall.

• SDR and PN pressure class
• PN6 HDPE pipe sizes
• PN10 HDPE pipe sizes
• PN16 HDPE pipe sizes

The inside diameter is the outside diameter minus twice the wall thickness, so it is not fixed for a size and changes with the pressure class: a 63 mm PE100 pipe has an inside diameter of 55.4 mm at 10 bar and 51.4 mm at 16 bar, and a 110 mm pipe 97 and 90 mm in the same two classes.

The inside diameter is the bore the water actually flows through, so flow and velocity calculations must use it, not the outside diameter. In the pipe simulator you can pick any size and class and see the inside diameter, the water held per metre and the flow velocity for a flow rate you choose.

• PE pipe simulator

For an exact quotation, state the outside diameter in millimetres, the pressure class in bar or SDR, the material grade (PE100 or PE80), the supply form and the total length. Pipes from 20 to 110 mm are supplied in 50, 100, 200 m coils and pipes from 63 to 630 mm in 6 and 12 m bars.

If you only know the size in inches, or are not sure which pressure class suits your line, write what the pipe is for, the working pressure and the length of the route, and our team will suggest a size and class. For critical lines, the final choice of pressure class should be made with the line’s designer.

• Contact us for a quotation