Excavation Volume Calculator
Example: Excavation length: 20 ft · Excavation width: 15 ft · Excavation depth: 3 ft · Soil swell factor: 25 %
| In-ground (bank) volume | 33.33 |
| Loose volume to haul | 41.67 |
| Volume | 900 |
Worked example
A 20 by 15 foot dig going 3 feet deep is 20 x 15 x 3 = 900 cubic feet, or 900 / 27 = about 33.3 bank cubic yards in the ground. Common soil swells about 25% once excavated, so you will actually haul 33.3 x 1.25 = about 41.7 loose cubic yards. Sizing your dumpsters or truck loads on the loose number, not the bank number, is what keeps you from under-ordering hauling.
Frequently asked questions
What is soil swell and why does it matter?
Soil in the ground is compacted; once you dig and loosen it, it takes up more space, a difference called swell or the swell factor. It typically ranges from about 10 to 30% for common soils and higher for rock. You haul the loose volume, so ignoring swell under-orders your dumpsters or trucks.
What swell factor should I use?
Sandy or loose soil swells around 10 to 15%, common loam about 20 to 25%, dense clay 25 to 40%, and blasted rock much more. When unsure, 25% is a reasonable planning figure for typical dirt. Use a higher number if you expect clay or rock.
Does this account for sloped or benched sides?
No, this assumes a simple rectangular box. Real excavations often need sloped or benched walls for safety, which removes extra soil beyond the box. For a trench deeper than about 5 feet, sloping or shoring is an OSHA requirement, so add volume and plan protection accordingly.
How do I turn cubic yards into truck loads?
Divide the loose cubic yards by your hauler's capacity per load. A typical tandem dump truck carries roughly 10 to 14 cubic yards, and a small dumpster 10 to 20 cubic yards, so the loose volume divided by that capacity gives the number of loads or bins you need.