How to Use the Excavation & Backfill Calculator
Accurate earthwork takeoff is essential for budgeting trucking, compaction, and disposal fees. The key distinction is between bank (in-place) volume and loose volume: once soil is disturbed, it swells and takes up more space in a truck than it did in the ground.
Enter the excavation footprint and depth, then subtract the structure volume (foundation, footings) to find backfill quantity. The remainder is spoil — converted to loose volume using the swell factor for truck-load calculations.
Swell Factor by Soil Type
- Sandy soil: ~15% swell
- Clay / silty soil: ~25% swell
- Weathered rock: ~40% swell
Frequently Asked Questions
Divide loose disposal volume by your truck's payload volume. A 10 CY (7.6 m³) dump truck is common; a 14 CY (10.7 m³) semi-end-dump holds more. Confirm payload with your hauler.
Sandy and granular soils compact well and are often reused for backfill. Expansive clays are generally unsuitable as structural backfill near foundations — consult a geotechnical engineer for critical applications.