Manufacturers commonly describe the thickness of their liners in MILs or Gauges. Some use the terms interchangeably like they are the same. They aren't. MIL designated liners are 6-12% thicker than a Gauge designated liner for the same number. For example, a 25 MIL liner is about 12% thicker than a 25 Gauge liner. This guide shows the differences to give you a better understanding of what thickness liner you are buying.
Step by Step
20 units - A 20 Gauge liner is 0.0185 inches thick. A 20 MIL liner is 0.0205 inches thick or approximately 11% thicker than a 20 Gauge liner.
25 units - A 25 Gauge liner is 0.0223 inches thick. A 25 MIL liner is 0.0250 inches thick or approximately 12% thicker than a 20 Gauge liner. By comparison a dime is 0.0490 inches thick
30 units - A 30 Gauge liner is 0.0260 inches thick. A 30 MIL liner is 0.0275 inches thick or approximately 6% thicker than a 30 Gauge liner. or just under twice the thickness of a 25 MIL liner.aph here.
How to calculate pool gallons
Length x width x average depth x 7.5 for rectangle and oval pools or x 7.0 for kidney pools or x 5.9 for round pools