How depth and volume relate
Doubling the depth doubles the volume. On a 20 × 10 ft (200 ft²) area:
| Depth | Volume | +10% waste | Bulk order | ≈ Weight |
|---|---|---|---|---|
| 2 in | 1.23 yd³ | 1.36 yd³ | 1.5 yd³ | 1.92 t |
| 3 in | 1.85 yd³ | 2.04 yd³ | 2.5 yd³ | 2.89 t |
| 4 in | 2.47 yd³ | 2.72 yd³ | 3.0 yd³ | 3.85 t |
| 6 in | 3.70 yd³ | 4.07 yd³ | 4.5 yd³ | 5.78 t |
Going from 3 in to 4 in on this area adds 0.68 yd³ to the purchase. Before settling on a depth, try the alternatives in the calculator — the depth buttons change it instantly.
How far a cubic yard goes
Coverage is the reverse: one cubic yard (27 ft³) spread to a depth covers 27 ÷ depth-in-feet square feet.
| Depth | 1 yd³ covers | Metric |
|---|---|---|
| 1 in | 324 ft² | 30.1 m² |
| 2 in | 162 ft² | 15.1 m² |
| 3 in | 108 ft² | 10.0 m² |
| 4 in | 81 ft² | 7.5 m² |
| 5 in | 65 ft² | 6.0 m² |
| 6 in | 54 ft² | 5.0 m² |
How far a ton goes
Coverage per ton depends on density as well as depth. At the 105 lb/ft³ reference value for dry gravel, one US ton is about 19.0 ft³:
| Depth | 1 US ton covers (≈) |
|---|---|
| 2 in | 114 ft² |
| 3 in | 76 ft² |
| 4 in | 57 ft² |
| 6 in | 38 ft² |
Using your supplier's density changes these numbers; the yards-to-tons calculator shows coverage at 3 in for any density.
Choosing a depth
There is no single correct depth; it depends on what the gravel has to do and the size of the stone.
- Decorative cover
- Needs enough depth for stones to overlap and hide the ground or fabric. Larger stone needs a deeper layer than small stone.
- Paths and patios
- Walked on, so the layer must stay continuous as stones move. Edging helps keep a thinner layer in place.
- Driveways
- Built in layers. One supplier's published guidance for light residential use is 4–6 in total (2–3 in of #2 stone plus 2–3 in of #57), and 8 in or more for heavy use Port Aggregates. That is one supplier's guidance, not a standard.
- Compacted bases
- Design to a finished, compacted depth and add a compaction allowance; a gravel-roads manual prepared for the FHWA reports a 30% or greater volume reduction from compaction in many areas source.
Topping up existing gravel
For a top-up, the depth is only the layer you're adding. Adding 1 in to a 20 × 10 ft area needs 0.68 yd³ with 10% waste (≈ 0.96 tons) — a 1.0 yd³ order. Measure the existing depth at several points first; thin patches may need more than the average.
Metric equivalent
6 × 3 m at 7.5 cm is 18 m² × 0.075 m = 1.35 m³; with 10% waste 1.48 m³ (≈ 2.50 tonnes at 105 lb/ft³), so a 1.5 m³ order.