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Construction & Homeearthwork

Excavation Volume Calculator

Excavation volume with the swell factor applied. A hole of 36 cubic metres does not produce 36 cubic metres of spoil: loosened earth expands by 10 to 50 percent depending on the soil, and that is what has to be carted away.

Also called: excavation calculator, cut and fill volume.

m
m
m
m³
%
Volume in the ground
36

36 m³ in the ground becomes 45 m³ once dug, because loosened loam swells by 25%. That is 8 truck loads at 6 m³ each. Backfill shrinks when compacted, so more loose material is needed than the void it fills.

Volume once excavated
45
Swell factor
25
Truck loads
8
Compacted backfill needed
41.4
Approximate mass
54
On swell and shrinkage
Backfill shrinks when compacted, so more loose material is needed than the void it fills.
How this is calculated
Method and background

How this is calculated

The volume in the ground, called bank volume, is the hole. What comes out is larger because digging breaks up the compaction, and the swell factor varies from about ten percent for sand to fifty for broken rock. Trucking is costed on loose volume, so estimating from the hole dimensions understates the haulage. The reverse applies to backfill: compacted fill shrinks, so more loose material is needed than the void it fills.

earth in the ground is compacted; digging it loosens it, so the volume to cart away exceeds the hole
s
Swell factor

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a 6 by 4 by 1.5 metre excavation in loam

Length
6 m
Width
4 m
Depth
1.5 m
Soil
Loam
Truck capacity
6 m³
Side batter for stability
0%

Volume in the ground36

36 x 1.25; 45/6 rounded up

Open this example

rock swells by half

Length
6 m
Width
4 m
Depth
1.5 m
Soil
Broken rock
Truck capacity
6 m³
Side batter for stability
0%

Volume in the ground36

boundary: the largest swell factor

Open this example

Method and limits

What it assumes

  • Typical swell factors by soil class. Site conditions vary.

What it deliberately does not model

  • Swell factors are indicative; a site investigation gives the real figure.
  • Groundwater, shoring and access all affect the real cost far more than the geometry.
  • This is a quantity estimate, not an engineering design for an excavation.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

Why is there more spoil than the hole I dug?
Because earth in the ground is compacted and digging loosens it. The expansion runs from about ten percent in sand to fifty in broken rock, and haulage is charged on the loose volume.
How much backfill do I need?
More than the void, because it compacts. Ordering exactly the void volume leaves a shortfall once it is rolled.