A sized bed is a mattress and foundation set that is designed to fit in a specific size frame or room. The term refers to any standard-size mattress, including twin, full, queen, king, California king, and Eastern king sizes. A sized bed typically ranges from 39 inches by 75 inches (twin) up to 84 inches by 102 inches (California king). The term is often used in the context of furniture shopping or when discussing bedroom decorating, as it refers to a specific size and type of mattress that will fit well within a particular space.