Gravel is quoted two ways — by the cubic yard and by the ton — and the depth you need depends on what drives over it. Here is how to work out both figures, and the mistake that leaves people a load short.
Step 1: work out the volume
Volume is length × width × depth, with the depth converted from inches to feet. Then divide by 27 to get cubic yards, because that is how bulk material is sold.
For a driveway 40 feet long and 10 feet wide at 4 inches deep: 40 × 10 × (4 ÷ 12) = 133 cubic feet, which is 4.94 cubic yards.
Step 2: pick the right depth
Depth is the decision that matters most, and it is not one number:
- 2 to 3 inches — a garden path or a patio base
- 4 inches — a light-use driveway on firm ground
- 6 to 8 inches — a driveway on soft ground, or one that takes delivery trucks
- 10 to 12 inches — heavy vehicles, or clay that holds water
A proper driveway is usually built in two or three layers: a coarse base of larger stone, then a finer top layer that locks together. Each layer is compacted before the next goes down.
Step 3: convert to tons if your supplier sells by weight
Multiply cubic yards by the density. Common gravel and crushed stone run about 1.4 short tons per cubic yard, so 4.94 yards is roughly 6.9 tons.
That figure shifts with the rock and how wet it is. If your supplier quotes their own density, use theirs — it is the number they will bill you against.
Gravel Calculator
Enter the area and depth — get cubic yards and tons, with an adjustable density.
Open the gravel calculator →The load that disappears
The most common surprise on a gravel job is that the first delivery seems to vanish. It has not: on soft or unprepared ground, a good portion of the first layer is pressed down into the soil by the first vehicle that drives over it.
Two things prevent it. Add about 10% to the volume if the ground is soft, and lay a geotextile fabric under the stone. The fabric stops the gravel migrating into the soil and stops the soil pumping up into the gravel, and it costs a fraction of an extra load.
Ordering: yards or tons
Yards measure volume, tons measure weight, and the same pile can be quoted either way. Get both figures before you call, so you can compare two suppliers who quote differently without doing mental arithmetic on the phone.
Also worth asking: what a full load is for their truck. Ordering 6.9 tons when the truck carries 7 is one delivery; ordering 7.5 is two, and the second delivery fee often costs more than the extra stone.