Measure and purchase your fabric
Begin your project by purchasing outdoor fabric to use for your covers; however, if you have canvas drop cloths laying around your garage, you can use them to make slip covers for your chairs. The drop cloths are not water resistant, so if you decide to use them, remove them after each use so they do not develop mold or mildew from being exposed to moisture.
Measure the chairs to be certain you have sufficient fabric. The average resin chair is approximately 21 inches wide, 28-1/2 inches high and 19 inches deep.
Cut the fabric pieces according to the measurements for your chairs adding an additional 1 inch for seam allowances.
With right sides together, sew all of the pieces together with a 7/8-inch seam. Sew a 7/8-inch hem around the bottom of each cover as well.
Slip the covers right over the back and sides of the chair. They should hang all the way down to cover the legs of the chair.