Soil Compaction Calculator

Soil changes volume every time it changes state, and this calculator tracks all three: bank volume is what you have in the ground before you touch it, loose volume is what a truck hauls away after excavation fluffs it up, and compacted volume is what remains once it's placed and rolled. In-Place Volume is the only input Bank Volume responds to — it passes straight through — but Loose and Compacted Volume each apply their own percentage on top of it, via the Swell Factor and Shrink Factor sliders respectively. Soil Type does the most consequential work on this page even though it never appears as a chart bar of its own: picking Sand/Gravel, Clay, or Topsoil/Loam silently resets the optimum-moisture target (10%, 18%, and 15%), the dry density used for the water-weight math (105, 95, and 85 lb/cu ft), and the recommended lift thickness (12, 8, and 6 inches) all at once, because clay's fine particles hold far more water and compact in thinner layers than granular sand.

Water Needed only turns positive when Current Moisture sits below the soil's optimum — at the default 12% moisture with Sand/Gravel selected, the target is 10%, so the soil is already wetter than ideal and the calculator correctly reports zero gallons; switch to Clay and the same 12% reading is now 6 points under its 18% target, so Water Needed jumps into the thousands of gallons for a 500-cubic-yard fill. This tool does not account for proctor test results, lift-by-lift density verification, or weather-driven moisture loss between mixing and placement.