Soil Compaction Calculator: Free Online Swell and Shrink Estimator
Use our free soil compaction calculator to convert between bank, loose, and compacted soil volumes using swell and shrink factors. Designed for earthwork estimators, excavation contractors, and civil engineers, this tool is essential for accurate earthmoving calculations -- know exactly how much soil to order and how much to haul away. Enter your loose volume, swell percentage, and shrinkage percentage to get instant, accurate bank and compacted volumes.
How to use this calculator.
- Enter the loose volume. This is the volume of soil as it sits in the dump truck or stockpile -- the excavated, uncompacted state. This is typically the volume you order or haul.
- Set the swell percentage. Swell is the volume increase when soil is excavated. Clay swells 20-30%, sandy soil 10-20%, rock 40-60%. Use 25% as a starting point if you do not have geotechnical data.
- Set the shrink percentage. Shrinkage is the volume decrease when loose soil is compacted. Clay shrinks 20-30%, sand 5-10%. Use 20% as a conservative starting point for most soil types.
- Review your results. The calculator shows bank volume (in-situ undisturbed volume) and compacted volume (after mechanical compaction). Use bank volume to determine how much material was removed from the cut area. Use compacted volume to verify fill requirements.
How do you calculate soil compaction and swell volumes?
Soil volume relationships use swell and shrink factors to convert between the three states of soil: bank (in-situ), loose (excavated), and compacted (after placement and compaction).
Bank Volume (cu yd) = Loose Volume (cu yd) ÷ (1 + Swell% ÷ 100)
Compacted Volume (cu yd) = Bank Volume (cu yd) × (1 - Shrink% ÷ 100)
Where:
- Swell is the percentage increase from bank to loose. A swell of 25% means 100 bank cu yd becomes 125 loose cu yd when excavated.
- Shrinkage is the percentage decrease from bank to compacted. A shrink of 20% means 100 bank cu yd compacts to 80 cu yd.
- Load factor = 1 ÷ (1 + swell) represents the ratio of bank to loose volume. A 25% swell gives a load factor of 0.80.
Example calculation.
Let's convert a truckload of excavated soil to compacted fill.
Scenario: You have hauled 150 loose cubic yards of clay soil. The geotechnical report indicates 30% swell and 25% shrinkage.
- Calculate bank volume: 150 cu yd ÷ (1 + 30 ÷ 100) = 150 ÷ 1.30 = 115.4 cu yd (in-situ)
- Calculate compacted volume: 115.4 cu yd × (1 - 25 ÷ 100) = 115.4 × 0.75 = 86.5 cu yd
Result: Your 150 loose cubic yards of clay (about 12-15 dump truck loads) will yield approximately 87 compacted cubic yards of fill after placement and compaction. This is about 58% of the originally trucked volume. Always account for this significant volume reduction when estimating fill requirements.
Tips from the field.
- Get geotechnical data early. The swell and shrink factors for your specific site soil can vary dramatically from rule-of-thumb values. A geotechnical report costs $2,000-$5,000 but can save tens of thousands in earthwork overruns on large sites.
- Track truck counts. On active earthwork sites, count every truckload in and out. Compare actual trucked volumes against your estimated volumes daily. A discrepancy of more than 10% between estimated and actual means your swell/shrink assumptions are wrong.
- Moisture changes everything. The same soil at different moisture contents has different swell and compaction characteristics. Soil that is too dry or too wet will not achieve specified compaction. Optimum moisture content (typically 8-15%) is critical.
- Rock changes by blasting method. Blasted rock swell varies with fragmentation size. Well-fragmented rock (small pieces) swells 35-45%. Poorly fragmented rock (large boulders) swells 50-70% due to larger void spaces. Blasting specifications affect your earthwork quantities.
Disclaimer: This calculator provides estimates for planning purposes only. Swell and shrink factors vary significantly based on soil type, moisture content, compaction method, compactive effort, and lift thickness. Always use site-specific geotechnical data for final earthwork estimates. PavementCalculator.com assumes no liability for earthwork quantity discrepancies.
Cost, price, and density figures on this page reflect approximate U.S. averages as of August 2026 and vary by region, supplier, and material availability.
Frequently asked questions.
What is soil swell and shrinkage?
Swell is the increase in volume when soil is excavated (loosened): typically 15-30%. Shrinkage is the decrease in volume when loose soil is compacted: typically 10-25%. Bank volume is the in-situ (undisturbed) volume. These factors are critical for accurate earthwork estimates.
How do I calculate compacted soil volume?
First convert loose to bank volume: bank = loose / (1 + swell%/100). Then apply shrinkage: compacted = bank x (1 - shrink%/100). For example, 100 cu yd loose with 25% swell and 20% shrink yields 80 cu yd bank and 64 cu yd compacted.
What are typical swell factors for different soils?
Clay swells 20-30% when excavated. Sandy soil swells 10-20%. Rock (blasted) swells 40-60%. Gravel swells 5-15%. Topsoil swells 15-25%. Always verify with local geotechnical data for accurate project estimates.
What is soil compaction and why does it matter?
Soil compaction reduces air voids and increases density, improving load-bearing capacity and reducing settlement. Proper compaction prevents foundation cracks, pavement failure, and uneven settling. Target 95% of maximum dry density per Proctor test for structural fill.
How is soil compaction tested?
Standard Proctor test: determines maximum dry density and optimum moisture. Field tests: nuclear density gauge (most common), sand cone test, or drive cylinder. Target is typically 95% of max dry density for structural fill. Testing ensures proper compaction for foundations and pavements.