How to Sew Outdoor Cushions

Measure the seat of the chair from front to back and side to side. Purchase upholstery foam to match those measurements. Place the foam on the seat of the chair and make any necessary size adjustments by marking the excess with a fabric marker and trimming it with a utility knife. Make a mark at the center of the back of the foam.

Spread the upholstery fabric on a flat work surface, wrong side facing up. Place the foam on the fabric and trace its outline with the marker. Make another mark on the fabric to show the center-back, aligned with the mark on the foam. Draw a new outline one-half inch outside the traced outline to allow for a seam, and cut with scissors. A one-half inch seam is recommended for upholstery projects by Upholster Magazine Online.

Place the cut piece on a fresh area of fabric, trace the outline and cut it. Repeat the center-back mark on this piece. Mark one piece as the cushion top and the other as the bottom.

Measure the thickness of the foam and add 1 inch to the measurement. Measure the circumference of the foam and add 2 inches. Place a ruler on the fabric and draw a straight line across to the circumference measurement, including the extra inches.

Measure up from the line to the thickness measurement, including the extra inch. Make several marks across the fabric above the first line. Place the ruler across the marks and connect them with the marker. Cut the strip along the lines.

Place the cushion bottom fabric right side up on a work surface. Align a long edge of the strip of fabric with the edge of the bottom, with right sides facing. Pin the strip to the bottom around the edges of the front, left and right. Sew a one-half-inch seam along the pinned edges; leave the back open.

Pin the cushion top fabric to the loose, long edge of the strip, aligning the edges. However, this time pin it all the way around to the center of the back. Sew a one-half inch seam. Turn the cover right side out.

Slip the foam into the cushion cover through the opening in the back. Fold the open, unsewn edges of the cover under one-half inch, toward the inside. Stitch them together by hand with a needle and thread to close the cushion.