Excavation Volume Calculator

Earthwork quantities are ambiguous unless the state of the material is stated, which is why excavation is tracked in three distinct volumes. Bank volume is the material in place, undisturbed in the ground, and is what the geometry of the hole gives: length times width times depth, divided by 27 to convert cubic feet to cubic yards. Loose volume is that same mass after digging, once the soil structure is broken and air voids open between the particles. Compacted volume is the material after it has been placed and rolled into a fill, and is usually smaller than the original bank volume. The swell factor converts bank measure to loose measure and governs hauling. Typical values are 10 to 15 percent for sand and gravel, 20 to 30 percent for common earth and loam, 30 to 40 percent for clay, and 40 to 60 percent or more for blasted rock. A 20 by 10 by 4 foot foundation dig is 29.6 bank cubic yards but roughly 37 loose cubic yards at 25 percent swell, which is four loads in a 10 cubic yard dump truck rather than three. Trucks are often limited by legal weight rather than heaped capacity, so wet or dense soil reduces the effective load. The simple prism formula also assumes vertical walls; the sloped or benched sides that trench safety rules require add volume that must be computed separately.

Systematic earthwork measurement grew out of nineteenth century railway construction, where balancing cut against fill determined whether a line was affordable to build. Surveyors computed volumes between cross sections using the average end area method and the more accurate prismoidal formula, both of which appear in engineering handbooks from the 1800s and are still implemented in modern civil design software. The mass haul diagram, which plots cumulative cut minus fill along a route to identify economical haul distances and borrow locations, comes from the same tradition. The distinction between bank, loose, and compacted measure became commercially important as mechanized earthmoving replaced hand and horse work in the twentieth century, since machine and truck productivity is quoted per hour in loose measure while designs are drawn in bank measure. Caterpillar has published swell and shrinkage tables for common soil classes in its Performance Handbook since the 1960s, and comparable tables appear in U.S. Army Corps of Engineers and Bureau of Reclamation earth manuals. Soil classification systems, notably the Unified Soil Classification System developed by Arthur Casagrande during the Second World War and later standardized as ASTM D2487, gave those swell values a consistent vocabulary, so that a stated percentage for clay or gravel means the same thing across contractors and specifications.