Backfill & Spoil Calculator

Backfills the excavation: distinguishes compacted backfill (in-place volume), loose fill (material to be hauled in) and surplus spoil (material to be hauled off).

Disclaimer：Results are produced by deterministic formulas and are intended for quantity estimating and option comparison only. A qualified engineer must verify them against the project specification, design documents and actual site conditions before use. The author accepts no liability for any loss arising from their use.

ASSUMPTIONS

RESULT

CALCULATION

METHOD

Compacted backfill V_b = V_exc − V_struct; loose fill required V_loose = V_b × compaction factor; surplus = V_exc × bulking factor − V_loose.

Compaction and bulking factors are empirical values; determine them from the soil type and compaction (Proctor) testing.
A negative surplus means the site-won material is insufficient and fill must be imported.

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