The short answer: a 10 by 10 ft area at 3 inches deep needs about 0.93 cubic yards of gravel, which is roughly 1.3 tons of crushed stone. Here is how to get there for any size.
The formula
cubic feet = length × width × depth in feet cubic yards = cubic feet ÷ 27 tons = cubic yards × tons per cubic yard
A 10 by 10 ft area is 100 sq ft. At 3 inches deep, that is 0.25 ft, so 100 × 0.25 = 25 cubic feet. Divide by 27 and you get 0.93 cubic yards. At 1.4 tons per cubic yard for crushed stone, that is about 1.3 tons.
How depth changes it
Depth is a straight multiplier. The same 10 by 10 ft area at 6 inches deep needs twice the gravel, near 1.85 cubic yards.
| Area | Depth | Cubic yards | Tons (crushed) |
|---|---|---|---|
| 100 sq ft | 2 in | 0.62 | 0.86 |
| 100 sq ft | 3 in | 0.93 | 1.30 |
| 100 sq ft | 4 in | 1.23 | 1.73 |
Buying by the yard or the ton
Bulk gravel is sold either by the cubic yard or by weight. The weight depends on the stone: pea gravel is lighter than crushed limestone, so the tons-per-yard figure is editable in the tool. Order about 5 to 10 percent extra so the surface compacts level and you are not short on the last pass.
Get your exact number
Enter the length, width and depth in the gravel calculator and it returns the cubic yards, the tons and the cubic feet. For a post-hole base or backfill, the concrete per fence post guide covers what goes around the post itself.