Stripping 200 m² of topsoil, 30 cm deep, clay soil
Bank volume is 60 m³; with a swell factor of 1.25, about 75 m³ of loose soil must actually be hauled away.
Earthwork volume calculator (excavation & backfill)
Result
Fill in the fields to see your result.
How it works
Soil in its natural, undisturbed state is called "bank" volume. Once excavated, it loosens and occupies more space — the "swell" — because digging breaks up its natural packing and introduces air gaps. This is the volume that actually fills a truck bed, so hauling calculations must use it, not the bank volume.
Backfill works the other way: loose fill material is compacted into place, and compaction reduces its volume by squeezing out air voids. To reach a target compacted (bank-equivalent) volume, more loose material must be ordered than that target volume alone would suggest.
Formulas used
In-situ (bank) volume
V = surface area × depth
Loose volume after excavation
V_loose = V_bank × swell factor
Loose fill needed for a compacted target
V_loose = V_compacted × compaction factor
Worked examples
Backfilling a 50 m² trench base to 40 cm compacted
The compacted target is 20 m³; with a compaction factor of 1.2, about 24 m³ of loose fill needs to be ordered.
Assumptions and limits
- The excavated or filled area is treated as a uniform depth over the whole surface.
- Swell and compaction factors are user-supplied estimates, not measured for a specific site.
- No allowance is made for slopes, benching or side-wall stability, which a real excavation plan must address.
Frequently asked questions
Why does soil take up more room once it’s dug up?
Undisturbed soil is naturally compacted by the weight of everything above and around it. Digging breaks that structure apart into loose particles with air gaps between them, so the same mass occupies a larger volume — exactly the way a packed suitcase takes up less room than its contents thrown loosely into a box.
What swell factor should I use?
It depends on the material: loose sand and gravel swell relatively little (around 1.10–1.15), ordinary earth is in the middle (1.20–1.30), and dense clay or rock swells the most (up to 1.30–1.40 or higher for blasted rock). When in doubt, use a geotechnical report for the site or ask the excavation contractor, since local conditions vary.
Updated