As a general rule I will never order less than 15 ton of rock from the quarry. I usually use 1.5 crusher run to fill in and dress existing residential driveways. Long country driveways I have to measure and calculate using the 75ft/truck rule.
If I am to build a driveway from bare dirt I will dig a few inches or so to hard pack soil. Put down 2 trucks of screenings for a roadbed and one layer of 2" screened on top. If I have too much 2" I build a crown into the roadbed to hide the excess and give the property owner something to scrape off later and fill erosion that has occurred over the last few decades. Do it right the 1st time. Its hard to get too much rock and build too solid of a roadbed. Take your sweet time, get it wet and pack the crap out of it.
If I am to build a driveway from bare dirt I will dig a few inches or so to hard pack soil. Put down 2 trucks of screenings for a roadbed and one layer of 2" screened on top. If I have too much 2" I build a crown into the roadbed to hide the excess and give the property owner something to scrape off later and fill erosion that has occurred over the last few decades. Do it right the 1st time. Its hard to get too much rock and build too solid of a roadbed. Take your sweet time, get it wet and pack the crap out of it.