Dirt is sold by the cubic yard. One cubic yard is a cube three feet on each side, 27 cubic feet, roughly what fits in the bed of a full-size pickup if you load it to the top of the sides. A dump truck carries ten to sixteen of them.
The formula
Measure the area in feet and the depth in inches, then:
cubic yards = length (ft) × width (ft) × depth (in) ÷ 324
The 324 is 27 cubic feet times 12 inches, folded into one number so you can measure depth in inches, which is how everyone thinks about it.
If the spot is not a rectangle, break it into rectangles and add them. If the depth varies, use the average, or measure at a few points and average those. Do not agonize. The truck does not deliver to the tenth of a yard.
Add for settling
Fill dirt is dumped loose. Once it is spread and rained on and walked on, it packs down and loses volume. Red clay fill, which is most of what you get around Birmingham, settles about 10 to 20 percent if nobody compacts it, and still a few percent if they do. Order 15 percent more than the formula says, and more than that if you are filling a hole you can never get a truck back to.
The calculator on this site adds the 15 percent for you.
Three examples
A low spot in a Hoover back yard
The spot that holds water is about 20 feet by 15 feet and needs to come up 6 inches on average.
20 × 15 × 6 ÷ 324 = 5.6 yards. Add 15 percent: about 6.5 yards. That is a single-axle load or a light tandem. Most yards have a minimum of five or six yards, so you are right at it.
A pad for a shed in Trussville
A 12 by 16 shed on a slope. One side needs 3 inches of fill, the other needs 14. Average depth about 8.5 inches, and you want the pad a foot bigger than the shed on every side, so 14 by 18.
14 × 18 × 8.5 ÷ 324 = 6.6 yards. Add 15 percent: 7.6 yards. Order 8. This is also a job where you want clay fill, compacted in two layers, because a shed is going to sit on it.
Backfilling an old pool in Pelham
A 16 by 32 foot pool, 4 feet in the shallow end and 8 in the deep end, averages about 6 feet of depth. Depth in inches is 72.
16 × 32 × 72 ÷ 324 = 114 yards before settling. This is where settling matters most, because a pool fill is deep and loose. Add 20 percent: about 137 yards, which is eleven or twelve tandem loads. Every one of them will want a clear path to the hole.
Turning yards into loads
| Truck | Carries |
|---|---|
| Single axle | about 8 yards |
| Tandem, the usual delivery truck | 10 to 14 yards, call it 12 |
| Tri-axle | 14 to 18 yards |
Dirt is heavy, 1.3 to 1.5 tons a yard and more when it is wet. A tandem is legally limited by weight before it is limited by space, so a load of wet clay may be 10 yards where a load of dry screened fill is 14. Ask the supplier what their truck actually carries.
Most of what you pay for is the truck, not the dirt. Nine yards and twelve yards often cost almost the same delivered, so if you are close to a full load, take the full load and use the extra to fix something else.
The two mistakes
The first is measuring the depth at the edge. The edge of a low spot is zero inches deep by definition. Measure in the middle and at a few points between, and average.
The second is forgetting the truck cannot get to the spot. A tandem needs about 12 feet of clear width, no low branches, and ground firm enough to hold 25 tons. If it cannot get to the hole, the pile lands at the closest point it can reach and the rest of the job is a wheelbarrow or a skid steer. Say so on the quote form. A supplier would rather send a smaller truck than get one stuck in your yard.
Questions people ask
How many yards of dirt in a dump truck?
Eight in a single axle, ten to fourteen in a tandem, fourteen to eighteen in a tri-axle. Weight limits usually decide, not the size of the bed.
How many wheelbarrows is a yard?
About nine to fourteen, depending on the wheelbarrow and how full you load it. A tandem load is well over a hundred. Rent a skid steer.
Does the supplier spread it?
Usually not; delivery means the truck dumps it where the truck can reach. Some haulers also do spreading and grading for an hourly rate. Ask when you get the quote.