From area to tons
Gravel is measured in three ways at once: you plan it in square feet, the quarry quotes it in cubic yards or tons, and the bags at the store are sold by the cubic foot. This calculator converts between all three, adds an allowance for compaction and gives a cost for bulk delivery.
The formula
- Volume (cu ft) = length × width × depth, with the depth converted from inches to feet (÷ 12).
- Cubic yards = cubic feet ÷ 27, then add the compaction allowance.
- Tons = cubic yards × density. Crushed stone weighs about 1.4 tons per cubic yard, river rock about 1.35, pea gravel about 1.3 and decomposed granite about 1.2.
Worked example: a garden path
A path is 20 ft long, 10 ft wide and needs 3 in of crushed stone.
- Volume: 20 × 10 × 3 ÷ 12 = 50 cubic feet.
- Cubic yards: 50 ÷ 27 = 1.85, plus 10% for compaction = 2.04 cu yd.
- Weight: 2.04 × 1.4 = 2.85 tons.
- At $50 a ton, the gravel costs about $143 before delivery, or you would need 110 bags of 0.5 cu ft.
Gravel by depth for the same path
| Depth | Cubic yards | Tons | Cost |
|---|---|---|---|
| 2 in | 1.36 | 1.90 | $95 |
| 3 in | 2.04 | 2.85 | $143 |
| 4 in | 2.72 | 3.80 | $190 |
| 6 in | 4.07 | 5.70 | $285 |
Each extra inch over 200 sq ft adds about 0.7 cubic yards. Depth matters more than most people expect, so measure it in several places on uneven ground.
Choosing the right depth
- Decorative beds and mulch replacement: 2 to 3 in of pea gravel or river rock over landscape fabric.
- Walkways: 3 to 4 in, ideally crushed stone that locks together under foot.
- Driveways: build in layers. A 4 to 6 in base of large crushed stone, then 2 to 4 in of smaller stone such as #57. Run the calculator once for each layer.
- Drainage trenches and French drains: clean, washed stone with no fines, so water can flow.
Bags or bulk?
Bagged gravel is convenient for under half a yard and costs nothing to deliver, but it is several times more expensive per ton. Above a ton, bulk delivery wins even with a delivery fee. Make sure the truck can reach the drop spot and that a driveway can take its weight.
Good to know
Densities vary from quarry to quarry and with moisture, so use the supplier’s figure when you have it. Round up rather than down: a second delivery for half a yard often costs more than the extra gravel.