How the calculation works
The formulas
Enter rectangular or cylindrical void dimensions. Bulking multiplies in-place excavation to obtain loose excavated volume. The fill factor is loose delivered volume per unit compacted volume, so it also multiplies the void.
Rectangular void = length × width × depth
Cylindrical void = π × diameter² ÷ 4 × depth
Loose excavation = in-place volume × bulking factor
Loose fill = target compacted void × loose/compacted factor
Assumptions to check
- Both factors are at least 1 and explicitly mean loose ÷ in-place or loose ÷ compacted. They are not percentages.
- The same void is assumed refilled. Soil suitability, batter slopes, support, and haulage are not designed.
A worked example
A 5 × 2 × 1 m void is 10 m³. At 1.2 bulking it yields 12 m³ loose excavation; at 1.15 loose/compacted fill factor it needs 11.5 m³ loose fill.