Driveways compact — order for it
A gravel driveway loses 20–30% of its loose depth to compaction and sinking in year one, so the working rule is <strong>order 4 inches to end up with 3</strong>. The calculator gives the tonnage at your entered depth; add the compaction margin on top when you call the quarry.
The three-layer driveway
Long-lasting driveways use a big base stone (item #4 or breaker run) under #57 crusher run, crowned in the middle so water sheds to the edges. Resurfacing annually with a thin layer of #57 is cheaper than rebuilding a muddy base — budget for a fresh yard or two every couple of years.