Quick answer: cubic yards = length × width × depth (ft) ÷ 27. But dirt does not stay that size. Digging swells it 20–25%, so a 10-yard hole yields about 12.5 yards to haul. Filling compacts it 20–30%, so a 10-yard void needs about 13 yards delivered.
Swell and shrink — the factor everyone forgets
Soil in the ground has been compressed for a very long time. Break it up and air enters the structure, so the same material occupies more space. Compact it back down and it shrinks again — but rarely all the way back.
| Soil type | Swell (dig) | Shrink (compact) | Loose yd³ per 10 dug |
|---|---|---|---|
| Sand / gravel | +10–15% | −5–10% | 11.0–11.5 |
| Loam / common soil | +20–25% | −10–15% | 12.0–12.5 |
| Clay | +25–40% | −15–25% | 12.5–14.0 |
| Rock (blasted) | +50–65% | −20–30% | 15.0–16.5 |
| Topsoil | +20–30% | −10–20% | 12.0–13.0 |
Two different jobs, two different corrections. Hauling away? Add the swell factor — that is the loose volume going in the trucks. Bringing fill in? Add the shrink factor — you need extra material because it will compress once placed. Getting these backwards is the classic excavation estimating error, and it goes wrong in both directions.
Truckloads and what they hold
| Vehicle | Volume | Weight limit | Practical load of dirt |
|---|---|---|---|
| Half-ton pickup | ~2.5 yd³ bed | ≈ 1,000 lb | Under ½ yd³ — weight-limited |
| Single-axle dump | 5–8 yd³ | ≈ 7 tons | 5 yd³ |
| Tandem dump | 10–14 yd³ | ≈ 15 tons | 10–12 yd³ |
| Tri-axle dump | 14–18 yd³ | ≈ 20 tons | 14–16 yd³ |
| 10-yard dumpster | 10 yd³ | 2–3 tons typical | Often 2–4 yd³ of dirt |
Note the pickup row. A truck bed that looks like it holds two and a half yards will be badly overloaded by one yard of damp dirt at 2,700 lb. Dirt hauling is almost always limited by weight, not volume — and the same applies to dumpsters, where "10 yard" describes the box, not what you are allowed to put in it.
Worked example: a basement excavation
A 30 × 40 ft foundation dug 8 ft deep, in common soil:
- In-ground volume: 30 × 40 × 8 = 9,600 ft³ ÷ 27 = 355.6 yd³
- Swell at 22%: 355.6 × 1.22 = 434 yd³ loose
- Truck count at 12 yd³ per tandem load: 434 ÷ 12 ≈ 37 loads
- Weight check: 355.6 × 2,700 lb ≈ 480 tons of material moved
Estimating on the in-ground figure alone would have booked 30 loads instead of 37 — a 23% shortfall that shows up as extra trips and extra cost on the invoice.
Common mistakes & pro tips
- Ignoring swell when hauling. The most expensive omission in excavation estimating.
- Ignoring shrink when filling. Order 20–30% more fill than the void measures.
- Using topsoil as structural fill. Organic matter decomposes and the ground keeps settling for years.
- Overloading by volume. Check the weight, not just whether it fits.
- Pro tip — call before you dig. Utility locates are free and legally required in most places. Book them days ahead of the machine.
- Pro tip — sloped or stepped excavations. Break the dig into sections and use the trapezoidal prism calculator for battered sides, which hold considerably more than a vertical-walled estimate.
Frequently asked questions
What is soil swell and why does it matter?
Soil expands when you dig it up, because excavation introduces air voids that were compressed in the ground. Sand swells about 10 to 15 percent, common soil 20 to 25 percent, and clay 25 to 40 percent. A 10 cubic yard hole therefore produces 12 to 14 yards of spoil to haul away — which changes the truck count, not just the arithmetic.
How many truckloads is my excavation?
Take the in-ground volume, add the swell factor, then divide by the truck capacity. A 100 cubic yard excavation in common soil swells to about 125 yards loose, which is nine or ten loads in a 12-yard tandem dump truck.
How much fill dirt do I need?
Calculate the space you need to fill, then order 20 to 30 percent more. Fill compacts as it is placed and rolled, so loose delivered dirt shrinks noticeably. Filling a 20 cubic yard void properly usually means buying 25 yards or more.
What is the difference between fill dirt and topsoil?
Fill dirt is subsoil — mineral, low in organic matter, and used for structural filling and grading because it compacts well and does not decompose. Topsoil is the biologically active upper layer used for growing. Never use topsoil as structural fill; it settles for years as its organic content breaks down.
How much does a yard of dirt weigh?
About 2,700 pounds for typical fill dirt at 100 lb per cubic foot, rising toward 3,000 pounds when wet or clay-rich. That is well over a ton per yard, which is why excavation hauling is priced by weight limits as much as by volume.