You should avoid buying a mattress that’s under 10 inches thick. A memory foam mattress thinner than 10 inches offers less durability and support. It is also less likely to contain a transition layer, which can add support, cushion, and responsiveness to a bed. If you want to pair a new mattress with an adjustable base, the ideal thickness range is 10 to 14 inches. If a mattress is thicker than 14 inches, it may have trouble adapting to the base’s movements, which can keep the bed from feeling comfortable.