A full size mattress, also known as a double mattress, measures 54 inches wide by 75 inches long. It provides ample space for single sleepers and is also suitable for couples who prefer to sleep closer together. This size is a popular choice for guest rooms and smaller bedrooms, offering a balance between comfort and space efficiency. Full size mattresses come in various types, including memory foam, innerspring, and latex. They are compatible with standard full size bed frames and can accommodate various bedding options, such as sheets and comforters. This versatility makes them a practical choice for many households.