Full-size mattress dimensions are 74L x 39W x 12H. This is the most common size in the market. It is used for small rooms and guest bedrooms. You can also use a full-size mattress on the floor of your bedroom or guest room. If you are planning to get a full-size mattress, turn to Mark’s Mattress Direct in  Grand Rapids, MI.  Whether you’re looking for a king mattress size, queen-size mattress, or full-sized mattress, you’ll find an extensive selection of various styles to suit your unique needs.