Earthwork / Volume conversion
Soil Swell and Shrink Calculator
Convert material volume between its bank, loose, and compacted states using the swell and shrinkage factors specified for your project.
Convert earthwork volumes
Enter one known volume and the project swell and shrinkage factors.
Known quantity and factors
Increase from bank volume to loose volume.
Decrease from bank volume to compacted volume.
Equivalent volumes
- Bank volume
- 100 m³
- Loose volume
- 125 m³
- Compacted volume
- 90 m³
Conversion factors
- Bank to loose
- 1.25 ×
- Bank to compacted
- 0.9 ×
- Loose to compacted
- 0.72 ×
Method
How earthwork volume conversion works
Bank volume describes material in its original, undisturbed position. Loose volume describes excavated or hauled material. Compacted volume describes placed and compacted fill. The calculator first determines the equivalent bank volume, then applies each factor from that common basis.
- Loose volume = bank volume × (1 + swell ÷ 100)
- Compacted volume = bank volume × (1 − shrinkage ÷ 100)
- Bank volume from loose = loose volume ÷ swell factor
- Bank volume from compacted = compacted volume ÷ shrink factor
Worked example
Example: 100 m³ measured in the bank
With 25% swell, 100 m³ of bank material becomes 125 m³ loose. With 10% shrinkage measured from the same bank quantity, its compacted volume is 90 m³. Converting directly from loose to compacted requires a factor of 0.72.
Factor selection
Use project-specific soil factors
Volume change depends on the material, its initial density, moisture, excavation method, handling, and compactive effort. FHWA guidance recommends using factors supplied through geotechnical information and notes that estimating values can vary materially. Confirm whether your project expresses a factor as a percentage, a multiplier, or a density relationship before entering it.
Scope
Assumptions and limitations
- Swell means the percentage increase from bank volume to loose volume.
- Shrinkage means the percentage decrease from bank volume to compacted volume.
- The same material mass is assumed across all three states.
- Losses, unsuitable material, over-excavation, settlement, and bulking variation are excluded.
- This tool does not predict moisture-driven movement in expansive foundation soils.
Common questions
Soil swell and shrink calculator FAQ
What is bank volume?
Bank volume is the volume of material in its original position before excavation. It is commonly identified as BCM or BCY.
Why are swell and shrinkage both based on bank volume?
A common bank basis prevents the percentages from being chained together. Loose and compacted quantities can then be compared consistently.
Can I enter a loose or compacted volume?
Yes. Select the known state and the calculator reverses the corresponding factor to recover bank volume before calculating the other states.
Does this calculate truckloads?
No. Truck capacity, fill factor, legal payload, and haul-cycle timing require separate inputs and belong in a haul-planning tool.