An armrest, or arm, is the raised structure at each end of a sofa that supports the sitter's arms and visually bookends the seating area. Armrests come in many shapes, from the rolled arm of a Chesterfield to the flat, angular lines of a tuxedo arm, and their width and height have a real effect on how much usable seat width the sofa offers.
Narrower, lower armrests generally leave more seating space for a given overall sofa width, which matters most in a small room, while wider, padded armrests add a comfortable place to lean or rest a drink. Our sofa styles guide covers how armrest shape relates to a sofa's overall style.