How deep should a gravel driveway be?

Typically 4 inches of compacted base for foot traffic and light vehicles, and 6 to 8 inches where trucks will run, often in two layers each compacted separately. Depth also depends on the subgrade: soft clay needs more than firm ground, and a geotextile fabric underneath stops the stone migrating into the soil.

Should I order by the ton or the yard?

Suppliers usually sell by the ton and you usually think in yards, which is why the conversion matters. Ask the supplier for the weight per yard of the specific material they are selling rather than relying on a general figure, because gradation and moisture move it more than most people expect.

Does rain change how much I need?

It changes the weight, not the volume. Wet aggregate can weigh 10 to 15% more per cubic yard than dry, so if you order by weight in the rain you receive less material than the same tonnage would give you dry. Order by volume where you can.

What waste allowance should I add?

Around 5 to 10% for spillage and uneven subgrade, which is trade practice rather than a published standard. Keep it separate from the compaction allowance, because they are different things and adding one to cover the other leaves you short.

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Gravel calculator: cubic yards, tons, and how much to add for compaction

This gravel calculator takes your area and depth and gives the volume in cubic yards and the weight in tons. It also adds a compaction allowance where the material needs one, which is the step that decides whether you order once or twice.

Length (ft)

Width (ft)

Depth (in)

Material

Compaction

How much extra gravel do you need for compaction?

More than most calculators tell you. The figure repeated across supplier sites is 20%, and for dense-graded base that is a lower bound rather than an answer.

Wisconsin's Department of Transportation ran a study on this in 2023 and measured expansion factors for aggregates ranging from 27% to 60%, with dense-graded base specifically at 34% to 52%. The Federal Highway Administration's earthwork tables imply something similar: you need roughly 1.3 to 1.5 loose volumes to end up with one compacted volume.

This calculator uses 30% for dense-graded material, which sits in the measured range rather than below it. If you are working to a specification, use the compaction figure in the spec, not ours.

Spec Wisconsin DOT WHRP report G22-05, December 2023, Weight-Volume Relationships and Conversion Factors for Soils and Aggregates. FHWA Federal Lands Highway, Earthwork Design tables. Checked August 2026.

Which materials actually compact?

Only the ones with fines in them. This is the distinction that catches people out.

Crusher run, dense-graded base, road base: a graded mix from dust up to about an inch. The fines fill the gaps between the larger stones and the whole thing locks together under a plate compactor. This is the material that needs a compaction allowance.

Clean stone such as #57: a single size with the fines washed out. There is nothing to fill the voids, so it does not densify meaningfully. Compacting it just settles it slightly. Adding 30% here would leave you with a pile of surplus stone.

The calculator applies the allowance only to materials that genuinely take it.

How much does a yard of gravel weigh?

Between about 1.2 and 1.85 tons depending on the material and how wet it is. The single number many calculators use, usually 1.4 tons per yard, is an average that is wrong for most specific materials.

Material	Tons per cubic yard	Compacts?
Crusher run / dense base	1.35 - 1.85	Yes
#57 clean stone	1.2 - 1.4	No
Pea gravel	1.3 - 1.4	No
Decomposed granite	1.4 - 1.5	Yes
Sand (dry)	1.3 - 1.4	Partly
River rock	1.2 - 1.35	No

Spec Wisconsin DOT Standard Specification section 305 gives 1.85 tons per cubic yard in place for dense-graded base. FHWA estimating tables give aggregate base at 139 lb per cubic foot. Density varies by quarry, gradation and moisture by up to a third, so confirm against your supplier's weight ticket.

Common questions

How deep should a gravel driveway be?: Typically 4 inches of compacted base for foot traffic and light vehicles, and 6 to 8 inches where trucks will run, often in two layers each compacted separately. Depth also depends on the subgrade: soft clay needs more than firm ground, and a geotextile fabric underneath stops the stone migrating into the soil.
Should I order by the ton or the yard?: Suppliers usually sell by the ton and you usually think in yards, which is why the conversion matters. Ask the supplier for the weight per yard of the specific material they are selling rather than relying on a general figure, because gradation and moisture move it more than most people expect.
Does rain change how much I need?: It changes the weight, not the volume. Wet aggregate can weigh 10 to 15% more per cubic yard than dry, so if you order by weight in the rain you receive less material than the same tonnage would give you dry. Order by volume where you can.
What waste allowance should I add?: Around 5 to 10% for spillage and uneven subgrade, which is trade practice rather than a published standard. Keep it separate from the compaction allowance, because they are different things and adding one to cover the other leaves you short.