An average 4-seater sofa has a width of 240cm; a height of 98cm and a depth of 95cm. Some brands measure it as 90″ seating width that does not work, including sofa arms. These average sofa sizes do not include recliners, footstools, sofa beds, or chaise loungers. This fact is important to keep in mind while purchasing a sofa for the home. Some of the bestselling items you can buy include Chesterfield Upholstered Sofa; Haven 2-Piece Terminal Chaise Sectional; and Ektorp by IKEA.