How this excavation calculator works
Working out how much dirt to dig comes down to one idea: volume = length × width × depth. Measure how long and how wide the excavation is, decide how deep you need to go, and multiply the three together. The result is the bank (in-place) volume — how much space the soil takes up while still packed in the ground. Bulk earthworks quote this in cubic yards (US) or cubic meters (metric).
The key is keeping units consistent. This tool converts your depth into the same unit as the length and width before multiplying, so a depth entered in inches is turned into feet first (divide by 12), and a depth in centimeters is turned into meters (divide by 100). If you are digging several identical areas, set the number of areas and the volume is multiplied accordingly. To get cubic yards, the calculator divides the cubic feet by 27 (1 cubic yard = 3 ft × 3 ft × 3 ft).
Dug soil does not stay the same size: it loosens and bulks up, which is called swell. The tool applies your swell percentage (default 25%) to the bank volume to estimate the loose volume you actually haul away, then divides that by the truck capacity (default 10 cu yd) and rounds up to estimate truck loads. Swell varies by soil — sand and gravel swell less than clay or rock — so adjust the percentage for your material.
Reference note: conversions use 1 cubic yard = 27 cubic feet and 1 cubic meter ≈ 35.31 cubic feet. Swell percentages and truck capacities are estimates that vary by soil type, moisture and equipment, so round up and always call to locate buried utilities and check local codes before digging.
Typical soil swell factors
| Material | Approx. swell |
|---|---|
| Sand / gravel | ~10–18% |
| Common earth / loam | ~20–25% |
| Clay | ~25–40% |
| Blasted rock | ~50–65% |
Typical dump truck capacities
| Truck | Approx. capacity |
|---|---|
| Small / pickup dump | ~1–3 cu yd |
| Single-axle dump | ~5–7 cu yd |
| Tandem-axle dump | ~10–14 cu yd |
| Tri-axle / large | ~14–18 cu yd |
Frequently asked questions
- How do I calculate excavation volume?
- Excavation volume is length × width × depth. Keep all three measurements in the same unit first — convert a depth in inches to feet by dividing by 12. That gives the bank (in-place) volume in cubic feet; divide by 27 for cubic yards. For example a 20 ft × 10 ft hole dug 2 ft deep is 20 × 10 × 2 = 400 cubic feet, about 14.8 cubic yards.
- How many cubic yards of dirt do I need?
- Find the volume in cubic feet (length × width × depth) and divide by 27, because a cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet. Dirt and fill are usually sold and hauled by the cubic yard, so this is the figure you give a supplier or hauler.
- What is soil swell or bulking?
- When soil is dug out it loosens and takes up more space than in the ground — called swell or bulking. Typical soil swells about 20 to 30 percent, so 10 cubic yards of bank material can become roughly 12 to 13 cubic yards loose. Swell varies by soil type, with sand and gravel swelling less than clay or rock, so treat the default 25% as a guide.
- How many truckloads of dirt is that?
- Divide the loose (hauled) volume by the truck's capacity in cubic yards and round up. A typical tandem dump truck carries about 10 cubic yards, while small trucks hold 5 to 6 and large ones 14 or more. Always use the loose volume, not the bank volume, because that is what fills the truck bed.
- What is the difference between bank and loose volume?
- Bank or in-place volume is how much space the soil occupies while still compacted in the ground — what you measure from the dimensions of the hole. Loose volume is the larger figure after the soil is dug and bulked up by the swell factor. Use bank volume to size the dig and loose volume to plan hauling and truck loads.
- How deep should I dig?
- Depth depends on the job: footings and foundations follow local frost-depth and engineering rules, utility trenches follow code for the line being buried, and a level pad is dug to subgrade plus base material. Always check local codes and locate buried utilities before digging, and allow for over-dig and sloped sides for safety.