For how many days and how many people? It is my husband who does not reapply as often, my 7yo and 5yo and me. I burn horribly. I read somewhere that on average you use 1oz per application. If we reapply 5 times a day between that would be two 10oz bottles a day at 15 full days, there is no way we would use 30 bottles of sunscreen! But how much? And yes I know Aruba has sunscreen and I even like it but would rather not spend the money when I can buy it on sale at home.