A gravel driveway should be at least 3 inches deep. The proper depth depends on the type of gravel used because finer gravel requires more depth than larger pieces of rock.
Most gravel driveways are between 3 and 8 inches deep. When a shallower depth is used, the gravel is more likely to scatter when it encounters foot or vehicle traffic. Additionally, a shallow driveway might need to be resurfaced more frequently.
The depth of a gravel driveway changes from the center to the edges. This is referred to as "grading." Most driveways are graded between 2 and 5 percent, with a maximum of 11 percent, to promote water runoff and to protect the surface.