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Excavation Calculator

Find the excavation volume.

How it is calculated

The tool treats the hole as a rectangular box: V = length × width × depth, giving the bank volume, that is, the soil measured in place before digging. It then multiplies by a fixed swell factor of 1.25 to estimate the loose volume, because dug soil takes up more space than undisturbed soil. Enter all three dimensions in metres; results are labelled in cubic metres and rounded to two decimals. Negative values return nothing. The 25% swell is a typical allowance only. Real swell depends on the soil type, so use a figure from your soil report if you have one. Sloped sides, steps and extra working space are not modelled.

Worked example

A trench is 10 m long, 4 m wide and 2 m deep. Bank volume = 10 × 4 × 2 = 80.00 m³. Loose volume = 80 × 1.25 = 100.00 m³. The 100 m³ figure is the one to use when sizing trucks or a spoil heap.

Try this example →

Common mistakes

  • Entering feet, centimetres or millimetres while the result is labelled cubic metres.
  • Using the bank volume to count truckloads; dug soil needs the larger loose volume.
  • Assuming the fixed 1.25 swell is right for every soil; clay, sand and rock behave differently.
  • Ignoring sloped sides, benching or working space that increase the real digging volume.
  • Forgetting that backfilled soil is compacted and may not return to its original volume.

About this calculator

This calculator finds excavation volume by multiplying length, width, and depth to get the in-place (bank) volume, then applying a swell factor to show how much more space that soil takes up once it's dug up and loosened — since excavated material always expands compared to its compacted, undisturbed state.

Construction estimators and excavation contractors use it to size how many truckloads of material will need hauling off site, and DIYers planning a pool, pond, or foundation dig use it to avoid underestimating how much dirt they'll actually need to move and store.

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