@Rachel Baranik I asked Bob about this and here is essentially what he had to say: Depth matters more than area. For 600 sqft you'll want about 4 inches deep, which is roughly 7 to 8 cubic yards. Anything thinner gets pushed around by tires and rain. Ask for "2A modified" or "2B" crushed limestone. It has fines in it that lock together when compacted, so it stays put. The clean stuff (like #57) looks pretty but migrates under tires. If you want a finished look, do 4 inches of 2A as the base, then 1 to 2 inches of #57 or #8 as the top coat. Put landscape fabric (geotextile) underneath before any stone. It's about 15 to 30 cents a sqft and it keeps the gravel from sinking into the soil over the first winter. Without it you'll be re-topping in 18 months. And edge it. Without edging, you're going to be raking gravel out of that lawn for the rest of your life. Treated landscape timbers or steel edging both work...timber's cheaper, steel lasts longer and reads cleaner from the curb. For supply, call local quarries and aggregate yards before Home Depot. Western PA has several smaller stone yards that deliver, and you'll usually pay 30 to 40 percent less than retail.