Worked example: 4 inches deep
| Step | Math | Result |
|---|---|---|
| Area | 20 ft × 20 ft | 400 sq ft |
| Volume at 4 in | 400 × 4 ÷ 12 | 133.3 ft³ |
| Add 10% for compaction | 133.3 × 1.10 | 146.7 ft³ |
| Cubic yards | 146.7 ÷ 27 | 5.43 yd³ |
| Tons | 5.43 × 1.4 | 7.60 tons |
Gravel by depth
| Depth | Cubic feet (+10%) | Cubic yards | Tons | Bulk order (tons) | Delivered cost | 0.5 ft³ bags |
|---|---|---|---|---|---|---|
| 2 in | 66.7 | 2.72 | 3.80 | 4.0 | $280 | 147 bags / $808 |
| 3 in | 100.0 | 4.07 | 5.70 | 6.0 | $370 | 220 bags / $1,210 |
| 4 in | 133.3 | 5.43 | 7.60 | 8.0 | $460 | 294 bags / $1,617 |
| 6 in | 200.0 | 8.15 | 11.41 | 11.5 | $618 | bags not practical |
| 8 in | 266.7 | 10.86 | 15.21 | 15.5 | $798 | bags not practical |
At 4 inches, a bulk delivery is cheaper here ($1,617 in bags versus $460 delivered). Bagged gravel weighs about 14,700 lb in total for this size, so bulk is the practical way to buy for a driveway.
Prices used: bulk gravel $45 per ton plus $100 delivery (1 ton minimum); 0.5 ft³ bags $5.50. Quarry prices vary widely by stone type and region.
Layering a 20 × 20 ft driveway
A new gravel driveway is built in layers. Using a 4 in base of large stone and a 2 in top of crusher run (6 in total) takes about 7.6 tons for the base and 3.8 tons for the top, 11.4 tons overall. To top up an existing driveway you usually need only 2–3 inches: 3.8–5.7 tons here.
Add a woven geotextile fabric on soft soil, and crown the center so water sheds. Order 10–20% extra for compaction on a new base.
Nearby sizes
Also see 100×12 driveway , 50×12 driveway, or the driveway and patio gravel chart. Open the gravel calculator to change the size or price.