Granite is sold by the square foot, so it will be helpful to have this information when pricing the material at various dealers. The cost of a granite countertop will, of course, depend on the size of your surface area. However, the average granite countertop will cost approximately $50 to $100 per square foot. In addition to the size, the cost will also depend on how thick you want the slab to be. One way to reduce the cost of a granite countertop is by purchasing your choice through a wholesaler. These companies will often charge a customer less than a home improvement store for the cost of installation and materials.