There is no definitive answer to this question as it will depend on a variety of factors, such as the size and shape of your pool, the materials used in its construction, and the climate in which you live. That said, most experts recommend a liner thickness of at least 20 mils for in-ground pools and 28-30 mils for above-ground pools.

It depends on the material of your pool and the height of your pool. You should consult a professional about what thickness would be best for your particular situation.