Cut three pieces of polyester batting to cover the top portion of your stool. Or, to use foam, set the stool upside down on the foam, and mark a circle that is the same size as the seat of the stool. Use an electric knife to cut the foam circle.
Lay heavy fabric or vinyl face down on a large, flat surface. Put your stool, seat down, on top of the fabric to help you measure the amount of fabric needed for your particular stool.
Draw a circle around the seat of your bar stool using pencil on the fabric. Remove your stool from the work surface. Draw a larger circle several inches around the outside of the first circle to accommodate the foam or polyester batting seat cushion.
Cut out the fabric circle. If desired, cut a test piece out of inexpensive fabric before cutting the actual fabric for the seat.
Put the fabric circle right-side down on a flat work surface. Place the batting or foam on top of that. Set the stool on top of it all, making sure to center all the layers.
Pull the fabric up around the foam cushion or batting to the underside of your stool seat. Put one staple under the seat to hold the fabric. Go to the opposite side of your stool, pull up some fabric, and staple in place.
Keep working opposite sides of the stool until you have all the fabric stapled down on the bottom of your stool. Trim off excess fabric with your scissors.
To make the bottom of your bar stool neater, cut out another circle of fabric that is just 1 inch larger than the seat of the stool. Staple it to the bottom of your stool, turning under the raw edges as you go.