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Excavation Volume Calculator

Work out a rectangular excavation in cubic metres, then convert the in-situ volume into an estimated loose spoil volume with a visible, editable bulking factor.

In-situ m³Loose spoil estimateNo sign-up
Groundworks excavation measurement illustration

Calculate excavation volume

1. Measure the excavationUse metres for length, width and average depth.
2. Get in-situ volumeThe geometry is kept separate from spoil bulking.
3. Apply your factorReplace the example factor with project-specific data where available.
m
Measured length of the rectangular excavation.
m
Use a representative average only where the width is reasonably consistent.
m
Use metres. For varying levels, split the excavation into sections where practical.
×
1.25× is an editable example, not a universal soil factor. Replace it with suitable project/material data.
Why this stays editable: British Geological Survey guidance defines bulking as the volume change after excavation and notes that the factor is used to estimate material that must be stored or removed. The applicable factor depends on the material/geology.

How to calculate excavation volume

For a rectangular excavation, the base calculation is straightforward: multiply the measured length by width by depth, with every dimension in metres. That gives the in-situ volume before the ground is dug and loosened.

In-situ excavation volume = length × width × depth

Estimated loose spoil volume = in-situ volume × your chosen bulking factor.

Measure first

Use the actual excavation dimensions or current drawings. Do not mix millimetres and metres.

Separate geometry from bulking

Keep the measured hole volume visible before applying any material factor.

Verify removal capacity separately

Volume does not tell you the safe payload of a skip, grab lorry or tipper.

Worked example: 10 m × 1 m × 0.6 m

In-situ: 10 × 1 × 0.6 = 6.00 m³.

Using the editable 1.25× example factor: 6.00 × 1.25 = 7.50 m³ estimated loose spoil. That is a 25% increase in volume. The factor must be changed if better material- or project-specific information is available.

Why loose spoil can be larger than the hole

Excavated soil or rock no longer occupies the same compact in-situ structure once it has been broken up. The British Geological Survey describes the bulking factor as the ratio or percentage of that volume change and uses it for estimating the excavated material that may need storage or removal. This calculator therefore shows the factor as a separate input instead of hiding it inside the result.

Useful technical references

British Geological Survey — BGS Civils: bulking volume · HSE — Excavations

Do not turn cubic metres straight into skip or lorry loads

Loose spoil volume is only one part of removal planning. HSE notes that, depending on conditions, a cubic metre of soil can weigh more than 1.5 tonnes. Material type, moisture, contamination, vehicle payload, skip restrictions and safe fill level can therefore limit a load before the available volume is full.

Planning estimate only. This tool calculates rectangular geometry and an editable loose-volume estimate. It does not classify waste, assess excavation stability, design temporary works, determine safe haulage payloads or certify a skip size.

When one average width or depth is not good enough

  • Stepped excavation: calculate each level or section separately and add the volumes.
  • Changing trench width: use the dedicated trench calculator or split the run where dimensions change materially.
  • Sloping or irregular formation: do not force it into a simple rectangular box if that would materially distort the result.
  • Overdig: include it only when it is genuinely part of the excavation you expect to remove; do not add a hidden blanket allowance.

Continue the excavation planning workflow

Project plannerExcavation & Skip Planning GuideMove from in-situ volume to loose spoil and removal planning without confusing the quantities.GuideExcavation and Spoil GuideUnderstand in-situ versus loose volume and the role of bulking.Related calculatorTrench Volume CalculatorUse a trench-specific calculation for long, narrow excavations.Next-stage calculatorSkip Volume EstimatorUse a loose-waste volume as one planning input, then confirm supplier restrictions.

Frequently asked questions

How do I calculate excavation volume in cubic metres?

Multiply the measured length by width by average depth, with all three dimensions in metres. A 10 m × 1 m × 0.6 m excavation is 6.00 m³ in situ.

What is a bulking factor for excavated soil?

It represents the change in volume when ground is excavated and loosened. The applicable factor varies with the material and ground conditions, so this calculator keeps it editable.

Is 1.25× the correct bulking factor for every excavation?

No. It is an editable example value only. Use suitable geotechnical, project or material data where available rather than treating one factor as universal.

Can I use the cubic metre result to choose a skip or lorry?

Not by volume alone. Material density, moisture, payload limits, waste restrictions and safe loading can all affect the actual removal requirement.

What if the excavation changes depth?

Split it into sensible sections, calculate each section separately and add the in-situ volumes. This is generally more reproducible than forcing a strongly variable excavation into one average depth.