Measure the front, back, sides and arms of the chair to determine how much fabric you need for the cover. Add and additional 1 1/2 inches to the measurements for seam allowance and to allow the cover to slip easily over the chair. Cut the pieces out with sewing scissors. If you are using an upholstery-grade fabric, electric sewing scissors will make cutting the fabric easier.
With right sides together, pin the fabric pieces together along the edges. Sew the pieces together with a 5/8-inch seam along the edge of the fabric to create the cover. Turn the piece right side out.
Place the cover onto the chair, adjusting the cover so that the corners are aligned. Pull it down over the back and sides as well as the seat.
Turn the chair upside down and staple the fabric onto the bottom, all along the underside. This will help keep the cover from slipping off of the chair.