Pipe Expansion Formula

Pipe Expansion Formula

Finding the expansion of pipe is relatively easy using the formula for “linear expansion”. There are many reasons beside trade school to know these calculations and apply the knowledge gained into your building plans.

Here are the factors you will need to know in order find the change in length (ΔL – change of length)of a section of pipe for various temperatures. Please note all of the units will be metric in the following examples.

  • ΔT -(change of temperature)
    This is the difference between the initial temperature and the final temperature of the pipe.
  • L – Initial length of the pipe
  • a – Coefficient of linear expansion for the material.

The formula to find the thermal expansion of pipe would look like this:

ΔL = a L ΔT

Using the formula

To keep this simple (I know it can look confusing), lets suppose we need to find how much a 10m length of copper pipe will change given a 40C change in temperature. The coefficient of linear expansion of copper is 0.000017, so a=0.000017 for this example.

ΔL = 0.000017 x 10 x 40

ΔL = 0.0068m or 7mm

Material type

Coefficient of thermal expansion (a)



73.8 x 10-6



22.2 x 10-6



18.7 x 10-6


Cast iron

10.4 x 10-6



10.0 x 10-6



66.6 x 10-6



14.5 x 10-6


Glass pipe

4.0 x 10-6



16.6 x 10-6



12.0 x 10-6



28.0 x 10-6


PEX 02 barrier

140 x 10-6



24 x 10-6


Polyethylene (PE)

200 x 10-6


Polyethylene terephthalate (PET)

59.4 x 10-6


Polypropylene (PP)

90.5 x 10-6



110 x 10-6



77 x 10-6



13 x 10-6


Wood Framing

3.7 x 10-6