Gravel for a Driveway: Yards, Tons, and Depth

The core formula: square feet to cubic yards

Gravel is sold by volume (cubic yards) or weight (tons), but every calculation starts with volume. The formula is length times width times depth, with all three measurements in feet, then divide by 27 to convert cubic feet to cubic yards. The only trick is converting your depth from inches to feet first: divide the inch figure by 12.

Work a real example. A driveway 50 feet long by 12 feet wide is 600 square feet. At a 4-inch depth, that is 600 times 0.333 feet, which equals 200 cubic feet. Divide by 27 and you get 7.41 cubic yards before any waste allowance. Change nothing but the depth and the number moves fast: the same 600 square feet needs 5.56 cubic yards at 3 inches and 11.11 cubic yards at 6 inches. Depth is the variable that drives your order, so nail it down before you do anything else.

For odd shapes, break the area into rectangles and add them up, or for a rough circle (a turnaround, say) use 3.14 times the radius squared. A 20-foot-diameter circle is about 314 square feet.

Depth: how deep gravel actually needs to be

Depth depends on the soil and the load, not on a single magic number. Over firm, well-drained soil for light passenger-vehicle use, a finished gravel surface of 4 inches is a common minimum. The problem is that 4 inches of loose stone over soft ground will pump, rut, and disappear into the subgrade within a season.

For a driveway built to last, estimators think in layers, not one pour. A typical new build runs 8 to 12 inches total: a 4-to-6-inch base course of larger angular stone (often a crushed 2-to-3-inch rock or a dense-graded crushed base), then a 3-to-4-inch intermediate course, finished with a 2-to-3-inch top course of smaller crushed stone that compacts into a tight driving surface. Each layer should be compacted before the next goes down, and gravel compacts roughly 15 to 20 percent, so order against the loose volume you calculated. If the driveway carries heavy or commercial vehicles, increase base thickness and use a geotextile fabric over weak subgrade rather than just adding more stone.

Resurfacing an existing, stable driveway is the cheaper case: 2 to 3 inches of fresh top-course gravel is usually enough to renew the surface.

Converting cubic yards to tons

Many suppliers quote and bill by the ton, so you need a reliable conversion. Crushed stone and gravel typically weigh about 1.4 to 1.5 tons per cubic yard. Multiply your cubic-yard figure by roughly 1.4 to 1.5 to get tons, or divide tons by about 1.45 to get back to cubic yards (so 1 ton is close to 0.69 cubic yard).

Using the example above, 7.41 cubic yards at 1.45 tons per cubic yard is about 10.7 tons. Treat this as an estimate: actual weight shifts with the stone type, gradation, and especially moisture, since wet material weighs more per yard. When a job is close to a delivery-truck capacity threshold, ask your supplier for the weight per yard of the specific product you are buying instead of relying on the average.

Coverage rates and a fast field check

A coverage rate lets you sanity-check an order without redoing the full calculation. One cubic yard of gravel covers about 162 square feet at 2 inches deep, about 108 square feet at 3 inches, about 81 square feet at 4 inches, and about 54 square feet at 6 inches. By weight, at the 1.45 tons-per-yard average, one ton of top-course stone covers roughly 110 square feet at a 2-inch depth.

To use these: divide your total square footage by the coverage number for your depth. The 600-square-foot example divided by 81 gives about 7.4 cubic yards at 4 inches, matching the formula. If the two methods disagree by more than a little, you have a unit error somewhere, usually an inches-versus-feet slip on the depth.

Waste, ordering, and getting the measurements right

Always add a waste and compaction allowance on top of the calculated volume. For a straightforward rectangular driveway, 5 to 10 percent is standard; go to the higher end for irregular shapes, sloped sites, soft subgrade that will absorb the first layer, or spreading by hand where you lose material to overshoot at the edges. On the 7.41-cubic-yard example, a 10 percent allowance brings the order to about 8.15 cubic yards, or roughly 11.8 tons.

The biggest source of error is not the math, it is the field measurement: an off-by-a-foot width or an inconsistent depth across a long run throws the whole order off. Measure width in several places and average it, and account for any flare at the road or a turnaround. This is where capturing the area accurately pays off; a LiDAR scan with a tool like ProBuildCalc records the driveway footprint and feeds the square footage straight into a takeoff, so the only judgment call left is choosing the depth.

Two ordering notes. First, delivery is typically the same trip cost whether the truck is half or fully loaded, so it is usually cheaper to order slightly long than to pay for a second run for a yard or two. Second, prices are regional and move with fuel and stone type, so get a current per-yard or per-ton quote locally rather than budgeting off an old number; expect crushed driveway stone and delivery to vary meaningfully by market and haul distance (approximate, regional).