Measure the width of each section of your couch at the widest area. For instance, if the arm of your couch is tapered toward the back, measure the wider area at the front. Write down all measurements for each section of the couch.
Accommodate for any seams in the couch design. The Commercial Interiors Outlet, which provides supplies and information for fabrics and wallpapers, advises that each seam should have an allowance of an extra 2 ½ inches.
Add yardage for a repeating pattern. Denver Fabrics estimates 2 to 3 yards should be added to your calculations to allow for a repeating pattern on a sofa or couch.
Add all of the width measurements and allotments for seams together. Divide that number by 36 to obtain approximate yardage for the project.