Construction
Backfill Volume Calculator
Work out backfill needed by subtracting the buried structure volume from excavation volume.
The result is the volume of material needed to fill the space left after the buried structure is in place, measured in cubic m, before any compaction allowance is added.
Formula
Backfill volume = excavation volume minus volume of the structure buried in it, such as footings, pipes or tanks.
How it works
Take the hole's volume and subtract everything that stays buried inside it. What remains is the space to fill back. Add a compaction allowance when ordering, since loose fill settles and compacts below its loose volume.
Worked example
For example, with an excavation volume of 30 cubic m and a structure volume buried of 5 cubic m, the backfill volume is 30 minus 5, which equals 25 cubic m before any compaction allowance.
FAQs
Should I add compaction allowance?
Yes, typically ten to twenty percent extra, depending on material and compaction method.
What if the structure is larger than the hole?
That cannot happen in practice, so check the measurements if the result is zero.
Can excavated soil be reused?
Often yes, if it is suitable and free of debris, but unsuitable soil must be replaced with proper fill.
Rough estimate only — consult a licensed professional for structural work before building.
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