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Excavation Volume Calculator

Calculate dig volume in-situ and after swell, plus the truck loads to cart spoil away.

  • excavation
  • dig
  • volume
  • spoil
  • swell
  • bulking
  • earthworks
  • trench
  • truck loads

About Excavation Volume Calculator

Earthworks have a counter-intuitive twist: the hole you dig and the pile you end up with are not the same size. Soil sits compacted in the ground, but the moment you dig it out it breaks up and bulks — a phenomenon called swell — so the spoil heap, and the number of truck loads to remove it, are noticeably bigger than the excavation itself. This calculator handles both: the in-situ ("bank") volume of the dig, and the larger loose volume after a swell factor.

It also turns that loose volume into whole truck or skip loads, which is usually what determines the cost and logistics of getting the spoil off site. Swell varies a lot by material — sand barely bulks, clay and rock bulk heavily — so the tool offers quick presets alongside a slider, and reminds you that deep excavation is a genuine safety hazard, not just a volume problem.

How to use

Choose metric or imperial and enter the length, width, and depth of the excavation. Set the swell factor with the slider, or tap a material preset — roughly 12% for sand, 25% for common earth, 35% for clay, and 50% for rock. If you're carting spoil away, enter your truck or skip capacity to get the number of loads.

The results show the in-situ volume (the hole) and the loose volume (the spoil heap after swell), each in cubic metres and cubic yards, plus the truck-load count when a capacity is given. Remember the relationship reverses for backfill: loose soil compacts back down, so you'll need to bring in a little more than the void to make up the final level. And treat the safety notice seriously — collapse risk, shoring, and locating buried services all sit outside what a volume figure can tell you.

Frequently asked questions

  • How do I calculate excavation volume?

    For a rectangular dig, multiply length × width × depth. A 4 × 3 m pit dug 1 m deep is 12 m³ in the ground. That's the in-situ or "bank" volume — the size of the void. For ordering skips or trucks you need the loose volume instead, which is larger because the soil bulks up once it's dug; this calculator shows both.

  • What is soil swell or bulking factor?

    When soil is excavated it loosens and takes up more space than it did compacted in the ground — that increase is the swell or bulking factor, given as a percentage. Sand bulks only about 10–15%, common earth around 25%, clay roughly 30–40%, and broken rock 50% or more. So 12 m³ of common earth in the ground becomes about 15 m³ of loose spoil to heap up and haul away.

  • How many truck loads of soil will I have?

    Divide the loose (swelled) volume by your truck or skip capacity and round up. Fifteen cubic metres of loose spoil into a 10 m³ truck is two loads. Always use the loose volume, not the in-situ figure — sizing trucks off the bank volume is a classic way to end up one load short, and the swelled soil simply won't fit in the space the calculation assumed.

  • Does swell matter when I'm backfilling?

    Yes, but in reverse. Loose soil compacts back down when you replace and compact it, so a given volume of loose spoil fills a smaller void than it occupied as a heap. If you're backfilling a trench or pad you'll generally need to bring in extra material to reach the finished level, because the excavated soil alone — once recompacted — won't quite fill the space it came out of.

  • Is deep excavation dangerous?

    It can be lethal. Trench and excavation walls collapse without warning, and even a shallow collapse can bury and crush a worker. Excavations beyond a modest depth require battering back the sides, benching, or installing shoring, and you must locate buried gas, power, and water services before digging. This tool estimates volume only — follow your jurisdiction's occupational-health rules for excavation work.

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