Work out backfill quantity instantly with clear inputs, formula shown and shareable results.
Backfill is the excavation less whatever the structure occupies. Because material is delivered loose and placed compacted, the compacted requirement is multiplied by a loose-to-compacted factor of about 1.15 for graded granular fill before it is converted to tonnage.
Compacted backfill
V = excavation volume - structure volume
Import quantity
Loose m³ = compacted x factor; tonnes = loose x density / 1000
V = excavation volume - structure volume. Backfill is the excavation less whatever the structure occupies.
Sometimes, if it is granular, free of organics and can be compacted at its natural moisture content. Cohesive clays generally cannot be compacted reliably around a structure and are replaced.
This calculator takes 4 inputs: Excavation volume, Volume occupied by structure, Loose to compacted factor, Backfill bulk density. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.