Driveway Base Gravel Calculator
This driveway base gravel calculator sizes the base layer of a new gravel driveway: the tons of base rock to order, with an editable allowance, and the area of landscape fabric to lay underneath it.
Driveway base calculator
Results
Results appear here as you type.
How the base calculation works
base volume = length × width × thickness × (1 + allowance % ÷ 100)
base rock (tons) = base volume × density
fabric = length × width × (1 + overlap % ÷ 100)
The calculator starts with the road base preset at a planning density of 1.50 tons per cubic yard, a 15% allowance and 10% extra fabric for overlaps. All of them can be changed.
Worked example: a 60 × 12 ft driveway with a 6 inch base is 720 square feet and 13.33 cubic yards. With a 15% allowance that is 15.33 cubic yards, or exactly 23 tons at 1.50 tons per cubic yard, so you would order 23 tons. The fabric is 720 × 1.10 = 792 square feet.
Why the base layer matters
Surface stone laid straight onto soft topsoil or clay tends to be pushed down into it by tyres, which leads to ruts and mud. A base of compacted, angular rock spreads the load and gives the surface layer something firm to sit on. A common build is:
- Prepared ground: topsoil and roots removed, the subsoil shaped so water runs off.
- Landscape fabric (geotextile), where the ground is soft or wet, to keep the stone and soil apart.
- Base layer: angular rock with fines, such as crusher run, road base or Class 5, compacted.
- Surface layer: clean crushed stone such as #57.
How thick each layer should be depends on your soil and traffic; see the gravel driveway depth guide for planning ranges and their limits, and the types of gravel guide for the materials. Size the surface layer with the gravel driveway calculator, which can also do both layers at once.
Frequently asked questions
What gravel is used for a driveway base?
Base layers are usually angular crushed rock mixed with smaller pieces and stone dust, sold as crusher run, road base, dense grade aggregate, quarry process or Class 5 depending on the region. The fines fill the gaps between larger stones so the layer compacts firmly.
Do I need landscape fabric under gravel?
On soft, clay or wet ground, a separation fabric is commonly used to stop the stone mixing into the soil. Whether you need it, and which type, depends on your soil and drainage, so ask a local contractor or supplier. The 10% overlap is a planning assumption; use the overlap the fabric maker specifies.
Why is the allowance higher here than in the main calculator?
Base rock is compacted hard and some is pressed into the ground below, so the calculator starts at 15% rather than 10%. It is a planning default, not a measured rate; use your contractor’s figure if they give one.