A worked example: 10m × 5m × 2m excavation
Digging a 10m by 5m area to 2m deep removes 100 m³ of undisturbed (bank) soil — but once loosened, that same soil swells to 125 m³, the figure that actually determines how many truckloads are needed to haul it away.
The formula: bank volume, then a swell factor
Bank volume = length × width × depth, the straightforward geometric volume of the hole itself. Loaded volume = bank volume × 1.25, a commonly cited swell factor reflecting that loosened soil no longer packs as tightly as it did undisturbed.
A smaller trench, the same relationship
A 6m × 1m trench dug 1.2m deep removes 7.2 m³ of bank volume, swelling to 9 m³ loaded — the same 25% increase holds regardless of the excavation's size.
Why the swell factor varies by soil type
25% is a reasonable general planning estimate, but sandy soils typically swell less while clay soils can swell more — a project working with a specific known soil type should consult a geotechnical reference rather than relying on the generic figure.
Where this bank volume goes next
The bank volume — not the loaded volume — is what feeds into a cut-and-fill earthwork balance, since fill requirements elsewhere on site are also measured in undisturbed, in-situ terms rather than swelled terms.