A gravel driveway is one of the best value projects you can take on, but only if you order enough stone to build it in proper layers. Skimp on depth and the driveway ruts and potholes within a season. Here is how to work out exactly how much gravel a driveway needs.
Start with the area
The first number is the surface area of the driveway in square feet. Multiply length by width. A driveway 40 feet long and 12 feet wide is 480 square feet. If your driveway widens near the garage or has a parking apron, break it into rectangles and add them up.
Choose the right depth
Depth is where gravel driveways succeed or fail. A driveway is not one layer, it is usually two:
- A base layer of about 4 inches of compacted crushed stone that carries the weight
- A surface layer of 2 to 3 inches of smaller crushed stone that you drive on
That means a proper new driveway is around 6 inches of total gravel depth. For a simple refresh over an existing solid base, 2 to 3 inches of new surface stone is enough. For soft or clay soil, go deeper on the base and consider a fabric underlayment to stop the stone from sinking into the mud.
Convert to cubic yards
Once you have area and depth, the volume formula is the same one used for any loose material:
Cubic yards = (length ft × width ft × depth in ÷ 12) ÷ 27
For our 40 by 12 driveway at 6 inches deep: 40 times 12 times 0.5, divided by 27, is about 8.9 cubic yards. Then add 10 percent for settling and for filling the low spots in the subgrade, which brings it to roughly 10 cubic yards.
Cubic yards to tons
Quarries and many suppliers sell crushed stone by the ton, not the yard, so you need to convert. Crushed stone weighs about 1.4 tons per cubic yard.
For our driveway at 10 cubic yards: 10 times 1.4 is about 14 tons. When you call a supplier, having both numbers ready, the yards and the tons, makes ordering painless.
Which gravel to use
Use angular crushed stone, not smooth rounded gravel, for a driveway. The sharp faces lock together when compacted and stay put under tires. A “crusher run” blend of stone and stone dust makes an excellent compacting base, with a cleaner 3/4 inch crushed stone on top. Save smooth pea gravel for paths and decorative areas, where it does not have to bear weight.
Compact each layer
Ordering enough stone is only half the job. Spread and compact the base in one pass before adding the surface layer. Loose gravel that is simply dumped and raked will rut immediately. A rented plate compactor or a few passes with a heavy roller makes the difference between a driveway that lasts a decade and one that needs regrading every spring.
Let the calculator size it
Our driveway gravel calculator takes your length, width, and depth and returns both cubic yards and tons with the settling allowance built in, plus a cost estimate. For patios, paths, and other gravel projects, the gravel calculator handles any shape, and the pea gravel calculator is set up for decorative rounded stone.