How the gravel driveway calculator works
A gravel driveway that lasts is built in layers: big stone at the bottom to carry the weight, a middle layer that locks into it, and a surface of smaller stone with fines that packs hard. The calculator works out each layer's volume from your area and its finished depth, turns it into tons and rounds up to the half tons that quarries load.
Volume of a layer (cu yd) = area (sq ft) × depth (in) ÷ 12 ÷ 27
Clean stone (#3, #57) = cubic yards × 1.4 tons
Surface stone with fines (#411, crusher run) = cubic yards × 2.16 tons per compacted cubic yard
Tons to order = tons × (1 + extra %), rounded up to the next half ton
Fabric = area × 1.1
The 2.16 figure comes from Penn State's Center for Dirt and Gravel Roads, which estimates 0.04 tons of surface aggregate per square foot for a layer 6 inches deep after compaction (placed 8 inches loose). Clean stone has no fines to fill its gaps, so it settles much less; the 10% extra covers spreading and soft spots.
Worked example
A driveway 60 ft long and 12 ft wide is 720 sq ft. Each 4 inch layer is 720 × 4 ÷ 12 ÷ 27 = 8.89 cubic yards.
- Base, #3 stone: 8.89 × 1.4 × 1.1 = 13.7 tons, so order 14 tons.
- Middle, #57 stone: the same, 14 tons.
- Surface, #411: 8.89 × 2.16 × 1.1 = 21.1 tons, so order 21.5 tons.
That is 49.5 tons for 12 inches of stone, about four tandem truckloads, plus 792 sq ft of fabric.
Layer by layer
| Layer | Stone | Typical finished depth | Job |
|---|---|---|---|
| Base | #3 (1 1/2 to 2 1/2 in) or #2 | 4 to 6 in | Spreads the load over soft soil |
| Middle | #57 (3/4 to 1 in) | About 4 in | Locks into the base and drains |
| Surface | #411, crusher run or driving surface aggregate | 3 to 6 in | Fines pack into a hard, smooth top |
Stone names and sizes vary by state and quarry. Ask your supplier for the closest match; "crusher run", "crush and run", "item 4" and "road base" are all dense-graded stone with fines.
How much a ton covers
| Stone | 2 in deep | 4 in deep | 6 in deep |
|---|---|---|---|
| Clean #3 or #57 (1.4 t/cu yd) | 116 sq ft | 58 sq ft | 39 sq ft |
| Surface stone with fines, compacted (2.16 t/cu yd) | 75 sq ft | 38 sq ft | 25 sq ft |
Before you order
- Strip grass and topsoil, and dig down so the finished surface sits a little above the ground around it.
- On clay or wet soil, lay woven geotextile fabric first, overlapping seams by about a foot.
- Compact each layer with a plate compactor or roller before the next goes on.
- Shape the surface with a crown or cross slope. Penn State recommends 1/2 to 3/4 inch per foot, and Kansas LTAP about 4% (1/2 inch per foot).
- Check the truck's weight against your culvert, septic lines and any lawn it must cross.
Sources
- Penn State Center for Dirt and Gravel Roads: Driving Surface Aggregate technical bulletin (PDF), for placement depth, the 0.04 tons per sq ft estimate and crown
- Kansas LTAP, University of Kansas: Good Gravel Roads (PDF), for the 4% crown and surface gravel with 8 to 15% fines
- Select Sand & Gravel: how much a yard of crushed stone weighs, for clean crushed stone at 1.35 to 1.4 tons per cubic yard
Common questions
How many tons of gravel do I need for a driveway?
A 60 by 12 foot driveway (720 sq ft) with 4 inches each of #3 base stone, #57 stone and #411 surface stone needs about 14 + 14 + 21.5 tons, or 49.5 tons, including 10% extra. Dense surface stone weighs more per inch because it packs down.
How deep should a gravel driveway be?
A new driveway on soil is usually built 8 to 12 inches deep in two or three layers: large base stone, a middle layer of #57 and a surface of stone with fines. Refreshing an old driveway may need only 2 to 4 inches on top.
What is the best top layer for a gravel driveway?
Crushed stone with fines, such as #411, crusher run or driving surface aggregate. The fines fill the gaps so the stone packs hard. Kansas LTAP recommends surface gravel with 8 to 15% fines, and rounded pea gravel stays loose and rolls underfoot.
How much does a ton of gravel cover?
One ton of clean #57 stone covers about 115 sq ft at 2 inches deep. One ton of compacted surface stone with fines covers about 75 sq ft at 2 inches, using Penn State's 0.04 tons per sq ft for 6 inches compacted.
Do I need fabric under a gravel driveway?
On soft or clay soil, a woven geotextile stops the base stone from sinking into the mud and saves stone over time. On firm, well-drained ground it is optional.