Earthwork Calculator
Calculate bank, loose, and compacted volumes. Computes cut/fill volumes with swell and shrink factors for excavation planning. Bank, loose, and compacted…
Computes cut/fill volumes with swell and shrink factors for excavation planning. Bank, loose, and compacted volumes follow standard earthwork conversion methods.
How is Earthwork Volume Calculated?
Earthwork calculations account for the fact that soil changes volume when excavated (swell) and when compacted (shrink). Bank volume is the in-situ (undisturbed) volume, loose volume is after excavation, and compacted volume is after placement and compaction.
The swell factor represents volume increase when soil is excavated — typically 20-40% for clay, 10-15% for sand, and 50-70% for rock. The shrink factor represents volume decrease when soil is compacted — typically 10-15% for clay and 5-10% for granular soils.
Accurate volume conversion is essential for estimating truck loads (loose volume), fill requirements (compacted volume), and comparing cut and fill quantities. The average end area method or prismoidal formula is used for calculating volumes along linear alignments.
Formula: Loose Volume = Bank Volume × Swell Factor Compacted Volume = Bank Volume × Shrink Factor Load Factor = Bank Volume / Loose Volume
Example Calculation
Excavating 100 m³ of clay (bank volume) with 30% swell and 15% shrink. Loose volume = 100 × 1.30 = 130 m³ (truck capacity needed). Compacted volume = 100 × 0.85 = 85 m³ (volume after placement). You need 130 m³ of truck capacity to haul 100 m³ of in-place soil.
When to Use This Calculator
- Earthwork contractors estimating truck loads needed to haul excavated material by converting bank volume to loose volume
- Project managers balancing cut and fill quantities to minimize haul distances and off-site disposal costs
- Cost estimators calculating fill material import requirements by converting required compacted volume back to bank volume at the borrow source
- Site engineers verifying that excavated material volume (loose) is sufficient to achieve the required compacted fill volume after placement
Common Mistakes to Avoid
- Using bank volume for truck count estimation — excavated soil swells 10-70% depending on material; trucks must carry loose volume, not bank volume
- Assuming cut volume equals fill volume — soil shrinks 10-15% when compacted; 1000 m³ of bank cut produces only 850-900 m³ of compacted fill
- Using generic swell/shrink factors without site-specific testing — factors vary dramatically with soil type, moisture content, and compaction method; geotechnical testing is essential for large projects
- Ignoring moisture content — soil above optimum moisture content is harder to compact and may need drying; soil too dry requires water addition; both affect volume and cost
How to Interpret Results
- Bank Volume is the in-place quantity (length × width × depth) — this is what excavation contracts typically measure and pay against
- Loose Volume = bank volume × swell factor and sizes the hauling operation: divide it by truck capacity to get the load count (the default factor of 1.25 means the soil bulks 25% when dug)
- Compacted Volume = bank volume × shrink factor — with the default 0.9, every 100 m³ of cut yields only 90 m³ of compacted fill; if cut must balance fill, plan to import the shortfall
- Both factors are entered as direct multipliers, not percentages — typical swell multipliers are about 1.10-1.15 for sand, 1.25-1.40 for clay, and 1.5 or more for blasted rock; verify against the geotechnical report for large quantities
- The volume model is a rectangular box — for sloped or benched excavations, enter the average depth or split the work into rectangular sections and sum the results
Related Standards & References
- Caterpillar Performance Handbook — industry-standard swell and load factor tables for soils and rock
- ASTM D698 / D1557 — Standard and Modified Proctor laboratory compaction tests that define the target density for compacted fill
- Peurifoy & Schexnayder, Construction Planning, Equipment, and Methods — standard text for earthmoving volume conversions and fleet sizing
Frequently Asked Questions
What is the swell factor for common soils?
Typical swell factors: Sand 10-15%, Loam 20-25%, Clay 25-40%, Rock (blasted) 50-70%, Topsoil 20-30%. These values vary with moisture content, soil structure, and excavation method. Always verify with site-specific testing for large projects.
How many truck loads for excavation?
Divide the loose volume by truck capacity. For example, 1000 m³ bank volume of clay (30% swell) = 1300 m³ loose. With 10 m³ trucks: 1300/10 = 130 truck loads. Add 5-10% for spillage and incomplete loading.