How to Determine How Much Rock You Need for a Driveway

Whether you're laying a gravel driveway or pavement with a gravel base, calculating the correct amount of rock you need is essential. Driveways must have a strong foundation with sufficient depth to support heavy weight loads. If you're laying pavers or bricks, the rock foundation should fill 2/3 the depth of the foundation.

Tape measure

Instructions

- 1
  Stretch a tape measure across the length and width of the driveway. Multiplying these numbers will give you the square footage. For instance, a 10-foot-wide driveway that is 20 feet long is 200 square feet.
- 2
  Decide on the depth of the rock layer. A rock foundation should be at least 8 inches thick for a driveway. If the entire driveway is rock, the depth should be about 12 inches. Convert this number to the decimal fraction of a foot. For example, an 8-inch layer is .67 feet.
- 3
  Multiply the square footage by the thickness to figure the cubic feet. A 200-square-foot driveway with a .67-foot depth has 134 cubic feet.
- 4
  Divide cubic feet by 27 to convert it into cubic yards, as this is the unit of measure rocks are typically sold in.
- 5
  Add 10 percent to the total to factor in spillage or any slight adjustments you may make to the size.

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