Gravel driveway calculator

Why two layers

Gravel driveways are usually built with a coarse base that spreads the load and a finer surface that drives well. One supplier's published guidance for a light-use residential driveway is 4–6 in total: 2–3 in of large angular stone such as #2, then 2–3 in of smaller stone such as #57. It recommends 8 in or more for heavy use Port Aggregates. That is one supplier's guidance, not a standard; soil, drainage, climate and traffic all matter.

Each layer here has its own material, depth, density and compaction allowance. The plan area and waste allowance are shared, because both layers cover the same footprint.

Compaction allowance

Driveway stone is compacted, so the loose volume you order is more than the finished volume. A gravel-roads manual prepared for the Federal Highway Administration notes a “30% or greater reduction in volume” from ordinary compaction in many areas source; that corresponds to about 43% extra loose material. The 20% starting value in this calculator is a planning allowance, not a measured figure. Ask your supplier what they see for their product and change it.

Worked example: 60 ft single-car driveway

For layer choice, drainage and cost, read the gravel driveway guide.

Reading the result

Each line of the order sheet answers a different question. Read them in order: geometry first, then your allowances, then the quantity you can actually buy.

Per layer

Calculated volume, + compaction, + waste, purchase volume, weight and bulk order — separately for base and surface.

Total

Sum of both layers' purchase volume and weight.

Cost

Each layer's price × its quantity, if you enter prices.

What this calculator assumes

• Dimensions are the plan area that will actually be covered.
• Depth is an average across the area.
• Areas are flat; slopes aren't adjusted for.
• Both layers cover the same plan area.
• Depths are compacted depths; the compaction allowance converts them to loose volume.
• Each layer has its own density and compaction value.

It can't see your site or your supplier's stone. What the calculators cannot know · Full methodology

Common mistakes with this calculator

1. Forgetting compaction on compacted layers

   What goes wrong: Stone packs down. A 30% volume reduction needs about 43% more loose material than the geometric volume.

   How to avoid it: If your depth is the finished, compacted depth, set a compaction allowance. Leave it at 0 for loose decorative cover.

2. Using one material for both layers by default

   What goes wrong: Base and surface stone usually differ in size and weight.

   How to avoid it: Set each layer's material and density separately.

3. Treating tons and cubic yards as the same thing

   What goes wrong: Weight depends on the material. The same 2 yd³ is about 2.62 tons of dry sand but 3.38 tons of wet gravel at the reference values.

   How to avoid it: Convert with a density you can see — ideally your supplier's — using the yards-to-tons calculator.