The cost of gravel rock patio may vary with the type of rock you chose. The size of the rock does vary a lot with its type. Sometime the size of the rock chosen will depend upon the location where you wish to use it. The cost of the gravel rock is almost 20$ per square yard. You must have the measurement of your patio before you start the project. It will give you a clear idea that how much your patio cost when it comes to make gravel rock patio of the highest quality.