What does 20 mil mean?

When it’s time to replace the liner in your pool, you will most likely hear the term mil as it relates to the thickness of a liner.

A mil is a unit of measurement that is equal to one thousandth of an inch. Therefore, a 20 mil liner is equal to 20 thousandths of an inch and a 27 mil liner is equal to 27 thousandths of an inch. If you have a one inch tall stack of liner samples, there would be 50 20 mil pieces. By the same token, there would only be 37 27 mil samples in an inch tall stack of samples.

A good frame of reference is five standard sheets of copy paper are as thick as a 20 mil liner. A mil, however, is not the same unit of measure as a millimeter.

Even though it’s thicker, a 27 mil liner will not last any longer than a 20 mil liner. For more information about the durability of a liner, please click here and here.