The quick answer
To find how much gravel a driveway needs, multiply length × width × depth (all in feet) to get the volume in cubic feet, divide by 27 to get cubic yards, then multiply by the gravel’s density (about 1.4–1.5) to get tons. Add roughly 20% because gravel compacts as it’s driven on.
For a typical 40 × 10 ft driveway at 4 inches deep, that’s about 5.9 cubic yards or roughly 8.3 tons of crushed stone (with the compaction allowance included).
The formula
Cubic yards = length (ft) × width (ft) × depth (ft) ÷ 27. Depth in inches ÷ 12 gives depth in feet. Multiply the cubic yards by density to convert to tons:
- Crushed stone / #57: ≈ 1.4 tons per cubic yard
- Road base / crusher run: ≈ 1.5 tons per cubic yard
- Pea gravel: ≈ 1.3 tons per cubic yard
How much gravel per square foot?
At a given depth, gravel needed scales straight with area. Handy figures for crushed stone (≈1.4 t/yd³), before the compaction allowance:
| Depth | Tons per 100 sq ft | Cubic yards per 100 sq ft |
|---|---|---|
| 2 inches | ~0.86 tons | ~0.62 yd³ |
| 4 inches | ~1.73 tons | ~1.23 yd³ |
| 6 inches | ~2.59 tons | ~1.85 yd³ |
How deep should driveway gravel be?
| Situation | Depth |
|---|---|
| Topping up / resurfacing | 2 inches |
| Standard gravel layer | 4 inches |
| New driveway on firm ground | 6 inches |
| Soft or clay-heavy soil | 8 inches (in two layers) |
A long-lasting gravel driveway is usually built in layers: a coarse base (road base or larger crushed stone) topped with a finer driving layer such as #57.
Step by step
- Measure the driveway length and width in feet (for an irregular shape, split it into rectangles and add them up).
- Choose a depth from the guide above.
- Enter the numbers in the calculator and pick your gravel type.
- Keep the 20% compaction box ticked so you order enough.
- Round up and add your price per ton to estimate the delivered cost.