Backfill Quantity Calculator

Work out backfill quantity instantly with clear inputs, formula shown and shareable results.

About Backfill Quantity Calculator

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.

Formulas

Compacted backfill

V = excavation volume - structure volume

Import quantity

Loose m³ = compacted x factor; tonnes = loose x density / 1000

Worked example

With the default values below, Backfill Quantity Calculator returns Backfill to import of 185.72. Change any input above and every figure here is recalculated in your browser.

Inputs used

Excavation volumeminimum 0.01 m³: 120 m³
Volume occupied by structureminimum 0 m³: 35 m³
Loose to compacted factoraccepts 1–1.6: 1.15
Backfill bulk densityminimum 100 kg/m³: 1,900 kg/m³

Results

Backfill to import: 185.72 t
Compacted backfill required: 85.00 m³
Loose volume to deliver: 97.75 m³
Truck loads at 20 tonnes: 10

Step by step

1Values used
2Compacted backfill
3Import quantity
4Backfill to import= 185.72 t
5Compacted backfill required= 85.00 m³
6Loose volume to deliver= 97.75 m³
7Truck loads at 20 tonnes= 10

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Backfill Quantity figure worked out?

V = excavation volume - structure volume. Backfill is the excavation less whatever the structure occupies.

Can excavated material be reused?

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.

What values do I need to enter?

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.