Define the excavation envelope
Use the excavation length, width, and depth actually required around footings, walls, basement slabs, or piers.
Working space and side slopes should be added explicitly rather than hidden in a blanket waste factor.
Calculate bank volume
For simple rectangular excavation, bank volume = length × width × depth; divide cubic feet by 27 for cubic yards.
Complex foundations should be split into footing trenches, wall zones, pits, or basement areas to avoid double counting.
Separate permanent construction volume
Concrete, aggregate base, drainage stone, and other permanent materials displace part of the excavated space.
Approved backfill quantity should be calculated from the remaining void, not assumed equal to excavation volume.
Estimate haul-off
Haul-off starts with excavated material that will not be reused on site and may require a loose-volume conversion for trucking.
Keep unsuitable soil, topsoil, rock, and ordinary soil separate if disposal or reuse rules differ.