The futon frame is the foundation of a futon. The futon base supports the futon mattress, while optional arms act as headboard and footboard. Futon frames are available as three different types; bi-fold futons (2 fold), tri-fold futons (3 fold) and loveseat futons which are available in sizes similar to beds.
A bi-fold futon frame folds once along the length, dividing the futon into 2 halves, creating a futon sofa. Bi-fold futon frames are available in double and queen sizes. A tri-fold futon frame folds 3 times along the width, dividing the futon into thirds, creating a chair. Tri-fold frames come in twin and double sizes and are ideal for small spaces.
In addition to serving as a sofa and bed, a loveseat futon can act as a lounge chair. A loveseat futon uses a bi-fold frame which includes a hidden third deck and separate "ottoman" cushion. When used as a sofa the deck and cushion are stored away. When used as a lounge chair the deck and cushion are attached to the end of the sofa. Finally, when used as a bed the entire frame, including attached deck and cushion, is straightened. The loveseat futon is also suited to small spaces because its sofa is narrower than standard futons. Loveseat futons are available in twin, double and queen sizes.
The futon dimensions are similar to that of actual beds, but the futon can be a little larger. However, the two are measured differently. While beds are measured by width and length futons are often only measured by width. To complicate matters the width of the futon is comparable to the length of its bed equivalent. A double sized bed is 54" wide by 75" long and a double sized futon is approximately 80 inches wide. A queen sized bed measures 60" wide by 80" long and the queen sized futon is approximately 85 inches wide. As a futon sofa both sizes fit about 3 adults. As a bed both will hold 2 people, however the queen size offers more sleep space per person.
When choosing a futon frame look for a well constructed, sturdy frame made of strong wood or metal. Futon frames should be relatively easy to convert from sofa to bed, however it should be noted that larger frames will likely require more effort. There are many styles and finishes available; some include arms, others have legs and it's all a matter of personal taste.