Excavation volume calculator
These are volumes worked from the dimensions you enter, plus a swell you choose. Soil behaves differently wet and dry and does not read a spec sheet, so treat the spoil and tonnage figures as haulage estimates. This tool does not size shoring, set a safe batter, or judge ground conditions — get those from a competent person on site.
Enter the length, width and depth of the dig and the tool gives you the bank volume — the soil in the ground — then applies the swell to show the loose volume you cart away, and optionally a tonnage. Over-dig, swell and density are all editable so the numbers match your ground and your trucks.
Worked example
A trench 20 ft × 3 ft × 4 ft is 240 cubic feet, or 240 ÷ 27 ≈ 8.9 bank yards. With 25% swell that loosens to about 11.1 loose yards to haul. At a spoil density of 1.5 tons per loose yard that is roughly 16.7 tons — enough to size the bins before the machine arrives.
The formula
bank = L × W × D · loose = bank × (1 + swell)
The bank volume is a straight box: length times width times depth, divided by 27 to turn cubic feet into cubic yards. Over-dig scales that box up before anything else. Swell is applied last, because soil only expands once it is broken out — multiply by one plus the swell fraction to get the volume the truck sees.
Questions
- How do I calculate excavation volume?
- Multiply the length by the width by the depth of the dig. A trench 20 ft long, 3 ft wide and 4 ft deep is 240 cubic feet, or about 8.9 cubic yards in the ground. That in-ground figure is the bank volume; the pile you haul away is bigger because loose soil takes more room.
- What is the difference between bank and loose volume?
- Bank volume is the soil sitting undisturbed in the ground. Once you dig it, it breaks up and takes more space — that expansion is the swell, and the result is the loose volume you actually cart away. Common earth swells around 25 percent, so 10 bank yards becomes roughly 12.5 loose yards; the swell field is editable because it varies a lot with soil type.
- How many truckloads of spoil will a dig make?
- Work in loose volume, not bank — the truck carries the expanded soil. Divide the loose volume by the capacity of your bin or truck. Wet clay swells and weighs more than dry sand, so if you are billed by weight, enter a density and use the tonnage the tool gives.
- Should I add for over-dig?
- Often, yes. Hand and machine digs rarely hold the neat lines you draw, and battered trench walls take more than a vertical cut. The over-dig field adds a margin to the bank volume before swell, so both the dig quantity and the haul quantity carry it. Leave it at zero for a tight, shored excavation.
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