⛏️ Excavation Calculator
Calculate bank (in-situ), loose (hauled), and compacted volumes for excavation projects. Estimate truck loads needed and total cost based on volume and rate.
What is Excavation?
Excavation is the process of removing earth, rock, or other materials from a site to form a cavity or trench, typically to prepare land for a construction foundation, utility installation, landscaping feature, or underground structure. The volume of material removed — and how it changes when disturbed — is the core calculation in excavation planning. Accurately estimating this volume determines the number of truck loads required for spoil removal, the cost of hauling, and the amount of backfill material needed to restore or grade the site after work is complete.
Excavated soil does not retain the same volume as it occupied in the ground. This concept is captured by three volume states: bank (BCM), loose (LCM), and compact (CCM). Bank volume is the natural, undisturbed state. When soil is excavated and loaded into a truck, it expands 15–35% into loose volume — this "swell factor" means more truck loads are needed than the hole's volume alone would suggest. When the same soil is used as fill and compacted, it shrinks to compact volume, typically 5–15% less than bank volume. Understanding these conversions is essential for accurate earthworks cost estimation.
Excavation calculations require the geometry of the excavation (length, width, depth) and knowledge of the soil type, which determines the swell and shrinkage factors. Clay soils typically swell more than sandy soils when excavated. For sloped or irregular excavations, the volume calculation becomes more complex, often requiring trapezoidal cross-section formulas or averaging end areas. This calculator handles rectangular and trapezoidal excavations, computes all three volume states, estimates truck loads, and provides a cost estimate based on your entered rate per cubic yard.
Frequently Asked Questions
Bank (BCM) is the volume of soil as it sits undisturbed in the ground. Loose (LCM) is the expanded volume after excavation — soil swells 15–35% when disturbed. Compact (CCM) is the volume after re-compaction (fill), which is typically 5–15% less than bank volume. These conversions are critical for hauling and fill calculations.
Clay: 30–40%, Sandy loam: 20–30%, Dense sand: 10–20%, Gravel: 10–15%, Rock (blasted): 30–50%. The default 25% covers most common soils. Always use site-specific values when available from geotechnical reports.
For a trapezoidal excavation with slope H:V, the average width = bottom width + (slope ratio × depth). The volume uses the average cross-sectional area. This calculator automatically adds the slope volume to the rectangular base. For example, a 1:1 slope on a 5m wide, 2m deep cut adds 2m to each side at the top, giving an average width of 7m.
A standard 10-wheel dump truck holds 8–10 m³ (10–13 yd³) of loose material. Articulated off-road dump trucks (ADTs) hold 15–35 m³. Small 6-wheel trucks hold 4–6 m³. Always use loose volume (not bank) for truck load calculations since that is what fills the truck bed.
Real-World Applications
Common Mistakes
Soil Swell & Shrinkage Factor Reference
| Soil Type | Swell (BCM → LCM) | Shrinkage (BCM → CCM) |
|---|---|---|
| Sandy soil | 10–15% | 5–10% |
| Loam / topsoil | 15–20% | 10–12% |
| Clay | 20–30% | 8–15% |
| Gravel | 10–15% | 6–8% |
| Soft rock | 30–35% | N/A (non-compactable) |
| Hard rock | 35–45% | N/A (non-compactable) |
References
- Caterpillar Inc. Caterpillar Performance Handbook. Caterpillar, 2023.
- OSHA. Excavations Safety: Appendix B. Occupational Safety and Health Administration, 2022.
- Peurifoy, R.L. and Schexnayder, C.J. Construction Planning, Equipment, and Methods. McGraw-Hill, 2014.
- Nunnally, S.W. Construction Methods and Management. Pearson, 2011.
- US Army Corps of Engineers. Engineering and Design: Earthwork. USACE, 2020.
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