He says the average sized driveway is about 20-by-20 feet, which requires about 13 tons of crushed rock and costs $1,300 to $1,500, including materials and labor. Schott estimates the average cost for him to install a gravel driveway is $1,200 to $1,500. According to CostHelper, the prices range drastically, from as low as $300 to thousands of dollars. A 12-by-25-foot driveway, with at least 4 inches of gravel, can cost about $300 to $1,000.