Sofas generally conform to a few standard widths and lengths; for instance, 72 inches is a standard length for a three-person sofa. However, sofas do not conform to one specific standard depth. The depth of a sofa varies between manufacturers and brands and isn't based on the length or height of the sofa.

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A sofa's depth determines how comfortable it is for sitting and sleeping.

Average Sofa Depths

Average sofa depth falls within a fairly large range between 31 and 36 inches; however, some sofas measure up to 40 inches deep. The disparity in the depth of sofas is due to the different ways in which they are constructed. Some sofas have a back that leans backwards at an angle; others have a straight back and still other sofas have wider back cushions that add to the sofa's depth.

Large Sofa Depths

Many large sofas that seat three people have a depth of at least 33 inches due to the size of the rear cushioning. However, longer sofas do not always mean a deeper sofa. Loveseats often have depths up to 40 inches due to their design and cushioning. When shopping for the right sofa, always factor in all measurements before making your purchase. How to fit the sofa into your living room isn't the only, or most important, thing to consider.

Single Seat and Loveseat Sofas

Single-seat sofas and loveseat sofas do not have different depth measurements simply because they are a different size. The average depth for a single seat and loveseat sofa is 36 inches and goes as low as 31 inches or as high as 40 inches. Sofa sets typically feature sofas of the same depth, although one may seat three people and the other only seats two. Recliners are usually deeper than large sofas and require additional space behind them for the sofa chair to recline. Today that depth is as low as 2 inches due to the design of the recline mechanism.

Depth and Comfort

Sofa depth is often equated with comfort because a deeper sofa potentially has a thicker, more cushy back cushion. While depth often gives an idea of how thick the back cushioning is, it is not the best way to understand comfort. Some manufacturers list the cushion thickness or foam density along with their depth measurement. This cushion measurement is much better in determining the comfort of the sofa.