Decide how full you would like your cushions to be. You can fill your cushions in several different ways. The two easiest ways to fill your cushions would be with a piece of foam cut to size or with a thick synthetic poly-fill. The fullness of your cushions will determine how much material you need to add to each side of your cushion pattern.
Measure each side of the chair for which you are making a cushion and write down the measurements. Add half the thickness of your filler to each side of the measurements. For instance, if your cushion is 24 inches in the back, 24 inches for the right and left side, and 28 inches on the front, and you want the filler to be 2 inches thick, the final measurements for your pattern would be 25 inches, 25 inches, 25 inches and 29 inches.
Draw your pattern by drawing the front and the back lines first and adding the side lines. Cut out the pattern.
Double your fabric and pin the pattern to the fabric. Cut out the fabric around the pattern.
Place the right sides of the material together and pin the edges. The right sides of the material are the sides of material that will be the outside of your cushions.
Sew the seams for the sides of the cushions. Depending on what type of filler you are using, you will want to leave an entire edge open or a pocket the size of your hand for stuffing the cushion.
Stuff the cushion and sew the opening shut. It will probably be easier to sew the opening closed by hand.