A cubic metre of soil is three different volumes in the course of a single day, and every quantity on an earthworks job belongs to exactly one of them. Name them before anything else.

Bank measure, $V_B$, is the material undisturbed, still in the ground, as the survey found it. Loose measure, $V_L$, is the same material after the bucket has broken its packing — bulked up with air, and larger. Compacted measure, $V_C$, is what it becomes in a finished embankment once the roller has squeezed it tighter than it ever was in the ground — smaller than bank. The trade abbreviates them BCY, LCY and CCY, and the letters are worth learning even in metric practice, because the concept travels and the units do not.

Swell: $V_L = V_B\left(1 + \dfrac{S}{100}\right)$, read aloud V-L equals V-B times one plus S over one hundred, where $S$ is the percent swell — about 25 % for common earth, 12 % for sand, 50 % or more for blasted rock. Shrinkage: $V_C = V_B\left(1 - \dfrac{S_h}{100}\right)$, where $S_h$ is the percent shrinkage, typically 10–15 % for common earth. Both are quoted against bank measure, always — bank is the hub, and the other two states each hang off it.

Now the rule that decides truck counts: the survey measures bank, the trucks carry loose, the embankment is built compacted. A haul box does not know what the ground used to look like. Hand a haulage contractor a bank figure and the fleet arrives short by exactly the swell — a quarter of the job, every day, until somebody counts the loads.

And the arithmetic trap, which costs more than the concept does. Going backwards, you divide, and dividing is not the same as flipping the sign on the percent. Undoing a 25 % swell means dividing by 1.25, which removes 20 %, not 25. Undoing a 12 % shrinkage means dividing by 0.88, which adds 13.6 %, not 12. The gap looks small on paper and it is the last few loads that never turn up.