A worked example: 150 m³ cut, 100 m³ fill
A site with 150 m³ excavated (cut) and only 100 m³ needed elsewhere for fill has a net volume of 50 m³ — a surplus that needs to be exported off-site.
The formula: net volume = cut − fill
A positive result means more soil came out of the ground than the site needs put back — surplus to export. A negative result means the opposite: not enough excavated soil to cover the fill requirement, so additional soil needs to be imported.
The other direction: a fill shortfall
A site with only 40 m³ cut but 70 m³ of fill needed has a net volume of −30 m³ — a shortfall requiring 30 m³ of soil brought in from elsewhere, the reverse situation from the surplus example above.
Why getting this balance right matters for project cost
Both directions cost money: exporting surplus soil means paying for hauling and disposal, while importing a shortfall means paying to source and truck in new material. Knowing the net balance in advance — rather than discovering it mid-project — lets a site plan transport and material costs ahead of time.
The one thing this comparison requires to stay accurate
Both the cut and fill figures need to be in the same terms — undisturbed (bank) volume, not the swelled volume that loosened excavated soil expands to. Mixing the two would overstate how much surplus (or understate how much shortfall) actually exists.