Soil Swell and Shrinkage Calculator

Bank is undisturbed soil sitting in place, also called in-situ or in-bank. Loose is that same soil after excavation, when it takes up more space because digging adds voids and air. Compacted is soil placed and rolled into fill, which takes up less space than the original bank.

It works from bank volume: loose equals bank times (1 plus swell fraction) and compacted equals bank times (1 minus shrinkage fraction). If you enter loose or compacted, it converts back to bank first, dividing by (1 plus swell) or (1 minus shrinkage) respectively, then derives the other two.

Swell is the volume increase from bank to loose, expressed as a percent. At 25% swell, 100 bank cubic yards become 125 loose cubic yards. Swell drives how many truckloads you haul, since trucks carry loose material.

Shrinkage is the volume decrease from bank to compacted. At 10% shrinkage, 100 bank cubic yards become 90 compacted cubic yards once placed and compacted in fill. It tells you how much bank material to dig to build a given compacted embankment.

Divide the loose volume by one plus the swell fraction. With 25% swell, 125 loose cubic yards divided by 1.25 equals 100 bank cubic yards. The tool does this automatically when you set the menu to Loose volume.

They depend on soil type, moisture and compaction effort, so the defaults of 25% and 10% are only a starting point. Sand and gravel swell less, dense clay swells more, and rock can swell 50% or higher. Use values from a geotechnical report or field tests for real work.

Compacted volume is bank times one minus the shrinkage fraction. At 100% shrinkage that factor is zero, and above it the volume goes negative, which is physically impossible, so the calculator rejects shrinkage of 100 percent or more.

The tool accepts a swell above -100 percent, so a small negative value is allowed mathematically, but real excavated soil almost always swells rather than shrinks. A negative swell would mean the loose pile is smaller than the bank, which is unusual outside special materials.

No. The calculation runs entirely in your browser, so the volumes and percentages you enter never leave your device and nothing is stored on a server.