Gravel Driveway Depth Calculator
A normal car driveway uses a 4-inch compacted base plus a 2-inch surface layer, for 6 inches total. Heavy trucks or soft soil often need 8 to 10 inches.
Your result
- Base gravel: — cu yd
- Surface gravel: — cu yd
- Total gravel: — tons
Quick answer
A normal car driveway uses a 4-inch compacted base plus a 2-inch surface layer, for 6 inches total. Heavy trucks or soft soil often need 8 to 10 inches.
How the calculator works
Base volume = length × width × (base depth ÷ 12) ÷ 27. Surface volume is the same formula with surface depth. Each layer is converted to tons using its own density.
How to build the two layers
Excavate to the finished depth, compact the subgrade, then spread the base stone in 2 to 3 inch lifts.
Compact each lift before adding the next. The surface layer goes on last and should be screeded and compacted lightly, not crushed into dust.
Why base stone and surface stone differ
Base stone includes fines that lock together under a plate compactor. Surface stone is cleaner, drains faster, and is more comfortable to drive on.
If you use one stone for both jobs, the driveway either stays loose or packs into a muddy surface.
Drainage and fabric
Crown the driveway slightly so water runs to the edges rather than pooling in the middle.
On clay or soft soil, use geotextile fabric between the ground and the base. It keeps the stone from mixing with mud and doubles the life of the base.
Note. Depth is measured after compaction, not loose. A 6-inch loose base can settle to about 5 inches.
| Use | Base | Surface | Total |
|---|---|---|---|
| Walking path | 3" | 1" | 4" |
| Car driveway | 4" | 2" | 6" |
| Light truck | 6" | 2" | 8" |
| Heavy truck / soft soil | 8" | 2" | 10" |
FAQ
How deep should a gravel driveway be?
At least 6 inches total for cars: a 4-inch compacted base and 2-inch surface layer.
Can I use one layer instead of two?
A single layer of clean stone will not lock together. A compacted base plus a surface layer lasts much longer.
Why does the base need different stone than the surface?
Base stone includes fines that compact into a solid layer. Surface stone is cleaner and drains better but does not lock by itself.
What happens if the gravel is too thin?
It ruts, mixes with soil, and pushes out at the edges. Thin driveways often need rebuilding within a season.
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Last updated: 2026-10-29