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Tons vs Yards: The Conversion Math

Gravel confuses buyers because it is measured in cubic yards but sold by the ton. One cubic yard is 27 cubic feet: length × width × depth in feet, divided by 27. To convert that volume to weight, multiply by the density of the stone. Average dry gravel runs about 2,800 lbs per cubic yard, or 1.4 tons, which is the figure this calculator uses. The exact number depends on the product: #57 washed stone weighs 2,700 to 2,800 lbs per yard (about 0.72 yards per ton), while crusher run, with its stone dust filling the gaps, weighs 2,900 to 3,000 lbs per yard (about 0.67 to 0.69 yards per ton). When you order, give the quarry both numbers: "I need 10 cubic yards, about 14 tons." That removes any confusion at the scale house.

Driveway Layers: Base First, Top Second

A gravel driveway is not one pile of stone spread flat. It is built in layers, and each layer has a job. The base layer is 4 to 6 inches of large, angular material, usually crusher run or 2 to 3 inch stone, and it carries the load and bridges soft soil. The top layer is 2 to 3 inches of smaller stone such as #57, which gives a smoother driving surface and locks into the base. Some builders add a middle layer to transition between the two sizes. Spread and compact each layer separately with a plate compactor or a loaded vehicle before adding the next. A single 8-inch layer dumped at once never compacts evenly and will rut within the first wet season.

The 10 Percent Compaction Allowance

Loose gravel in a truck bed is full of air. Once it is spread, wetted, and compacted, the stones settle into each other and the layer loses roughly 10 percent of its loose volume. If you order exactly the geometric volume, the finished driveway ends up thinner than planned. The fix is simple: calculate the volume, then add 10 percent before ordering. On the 150 × 12 ft driveway from the FAQs above, the raw math gives 22.2 cubic yards (about 33 tons of crusher run). Adding 10 percent takes the order to about 24.5 cubic yards, or 37 tons, which is the amount that actually finishes at a full 4 inches after compaction.

Choosing Stone Size and Type

Size and shape matter more than color. Angular crushed stone locks together under load, which is why #57 and crusher run dominate driveways. Rounded stone, pea gravel and river rock, rolls under tires like ball bearings and belongs in decorative areas instead. Match the product to the layer: crusher run for the base because its dust binds it into a near-solid pad, #57 for the top layer and for drainage work because its washed, uniform stones let water pass through, and larger 2 to 3 inch stone only where you need to bridge mud or fill a deep base. If you are unsure, tell the quarry the project and the layer, and they will usually steer you to the same two products.