When adding barstools to a counter or table, you need to bring legroom into the equation. You should leave about 10 inches between a seat and the counter or table. This distance is usually the most comfortable for someone of average height. To figure out how tall your chairs should be, grab a measuring tape, pencil, and paper. Measure from the floor to the top of the counter or table surface. Write down that number and subtract 10 inches to get the height of the stool you need for that space.
Remember to also measure the length of the counter to determine the number of stools that can fit in the space. A good rule of thumb is to allow 28 inches for each place setting.