A full size mattress, also known as a double mattress, measures 54 inches wide by 75 inches long. It provides enough space for one person to sleep comfortably or for two people who don’t mind being close together. This size is popular for smaller bedrooms, guest rooms, or for individuals who prefer a bit more room than a twin mattress offers. Full size mattresses come in various types, including memory foam, innerspring, and latex. They are designed to support different sleeping styles and preferences. When choosing a full size mattress, consider factors like firmness, material, and budget to find the best fit for your needs.