In-situ excavation and loose spoil are different volumes

Soil before excavation occupies an in-situ volume. After digging, the loose material can occupy more space. A planning tool can apply a user-entered bulking percentage, but it cannot determine that percentage from the excavation dimensions.

A worked example

Item	Example or check
Excavation	4 m × 2 m × 0.5 m
In-situ volume	4 m³
Illustrative bulking	20%
Loose spoil	4.8 m³

Check the assumptions

Label the percentage as bulking rather than general waste. It is a change in material state and packing, not a guarantee that some fixed amount will be thrown away. A quoted skip volume also does not establish the allowable weight or usable loading volume.

Separate soil types or project stages when the contractor expects different bulking behaviour. If the excavation has sloping sides, steps or irregular boundaries, a single rectangular formula will not describe it. Use an appropriate measured geometry and professional advice.

Before using the estimate

No excavation volume result makes a trench safe to enter. Utilities, soil stability, shoring, access, spoil placement and local requirements need qualified assessment.

Open the Excavation Calculator and compare your measurements with the example.