When talking about the “mil” or “guage” of vinyl pool liners, you should first get a decent understanding of what these terms actually mean. The most common term for vinyl, “mil” (not to be confused with millimeter) is a unit of measurement equal to one thousandth of an inch. Therefore, a 20 mil liner thickness is equal to 20 thousandths of an inch. The term “gauge” (not to be confused with mil), is a bit more of a moving target. See, multiple industries measure items such as wire, shotgun barrels, sheet metal, photographic film and hypodermic needles by their gauge. This can be very confusing as in a case like shotgun barrels where the smaller the gauge, the larger the barrel. This is not the case when it comes to vinyl pool liners where the higher the gauge, the thicker the material.

When shopping for pool liners, it is very important that you are aware that gauge is not equal to mil. Some manufactures or retailers like to offer their liners in terms of gauges because they sound ticker than a true mil. To be technical, a 30 mil liner is equivalent to 0.0300 inches. A 30 gauge liner is equivalent to 0.0260 inches (26 mil). Therefore, if you see a liner advertised at 35 gauge, it is truly a 30 mil liner. To avoid this confusion, always make sure and purchase from a company that advertises in mil, versus gauge.

To give some additional perspective, here is the mil of some everyday items:

When deciding what’s best between the thicknesses of vinyl pool liners for in ground pools, a variety of factors should be considered. Such as the location of the pool in relation to sun exposure, how much time the pool will spend covered and the type of surface the liner will be laid on.

If the pool will experience longer exposure to direct sunlight throughout the year or when you’re dealing with a rougher surface material, such as a concrete or a sand and concrete mixture, the appropriate, preferred mil of vinyl pool liner would be the 28-30 mil. Although thicker material will typically cost you about 5 – 10% more, it is 29 – 32% thicker than 20 mil, and will no doubt provide adequate thickness and protection for its purpose.

With that being said, all pool liner material, no matter the thickness will boast the smooth nature vinyl is famous for, come in an array of patterns to choose from, and in most cases, carry the same warranty.