Concepts · For everyone
Bank, Loose and Compacted Yards: Swell, Shrink and Why the Pile Never Matches the Hole
Dig a hole and the dirt that comes out won’t fit back in. That is swell, and it is why truck counts, pile scans and hole measurements never agree unless you convert them to the same kind of yard.
In short
- A bank yard is in the ground, a loose yard is in the pile or truck, a compacted yard is after rolling. Loose is the largest; compacted is usually the smallest.
- Swell: sand and gravel 10–18%, common earth about 25%, dry clay about 26% (load factor 0.79), dense clay 20–35%.
- 100 bank yards of clay becomes about 126 loose yards on the truck and about 90 compacted yards in the fill.
- Always convert through bank yards; never multiply a loose volume by a shrink factor. And agree which yard a bill is in before anyone digs.
Three kinds of cubic yard
Earthwork uses three units that all sound like “a cubic yard” and are not interchangeable. A bank cubic yard (BCY) is material in its natural, undisturbed state in the ground. A loose cubic yard (LCY) is the same material after it has been dug, in a truck or a spoil pile, with air mixed in. A compacted cubic yard (CCY) is the material after it has been placed and rolled, with that air driven back out and then some. By volume, loose is the largest and compacted is usually the smallest, which Propeller’s note on shrink and swell writes as compacted < banked < loose.
Every pile you can see is in loose yards. Every hole is in bank yards. Every finished pad or road base is in compacted yards. Most arguments about dirt come from comparing two of these as if they were one.
Swell factor and load factor
Swell is the percentage increase in volume from bank to loose. A material with 25% swell turns 100 bank yards into 125 loose yards. The load factor runs the other way: bank volume divided by loose volume, or 1 ÷ (1 + swell). Dry clay with 26% swell has a load factor of 0.79, so a 12-yard truck of loose clay carries about 9.5 bank yards. Reference tables such as the one at Civils.ai give typical values; the exact figure for a site depends on grain size, moisture and how the material was loaded.
| Material | Swell from bank to loose | Load factor (bank ÷ loose) | Shrinkage from bank to compacted |
|---|---|---|---|
| Sand and gravel | 10–18% | 0.85–0.91 | 0–15% |
| Common earth, loam | ~25% | ~0.80 | 10–15% |
| Dry clay | ~26% | 0.79 | 10–20% |
| Dense clay | 20–35% | 0.74–0.83 | 10–20% |
Typical planning values from estimating references. Grain size, moisture and loading method change them; test site soils for real quantities.
Shrinkage on compaction
Shrinkage is measured from bank too: compacted volume is bank volume times (1 − shrinkage). Sand and gravel compact back to roughly 85–100% of their bank volume, loams lose about 10–15%, and clays can lose 10–20%. This is why supplier guidance for a gravel base, such as SiteOne’s notes on calculating bulk materials, tells you to order 10–15% more than the finished volume you need. The loose yards on the truck will become fewer compacted yards in the ground.
A worked example: 100 bank yards of clay
A contractor digs a basement that measures 100 bank yards. With 26% swell, the spoil is about 126 loose yards: around ten tandem truckloads at 12–13 loose yards each, not eight. If the same clay is placed as fill and compacted with 10% shrinkage, it finishes at about 90 compacted yards. One excavation, three numbers, all correct.
| Stage | Unit | Volume | Factor applied |
|---|---|---|---|
| In the ground | Bank yards | 100 | — |
| In the trucks or the spoil pile | Loose yards | ~126 | × 1.26 (26% swell) |
| Placed and compacted | Compacted yards | ~90 | × 0.90 (10% shrink, from bank) |
Both factors are applied to the bank volume, never to each other.
Why you can’t chain the factors
It is tempting to take a loose volume and multiply by a shrink factor to get compacted yards. Don’t. Both swell and shrinkage are defined relative to bank, and as Propeller’s note points out, the relationship between the three states is not linear, so a factor applied to the wrong starting state gives the wrong answer. Convert loose to bank with the load factor first, then bank to compacted with the shrinkage. In the example above, 126 loose × 0.79 ≈ 100 bank, × 0.90 ≈ 90 compacted. Skipping the middle step and applying 0.90 to 126 gives 113, which is 25% too high.
The spoil pile is in loose yards
Any measurement of a pile, whether from a tape and the cone formula or from a phone scan, reports loose yards, because that is what a pile is. To compare it with the hole it came from, divide by one plus the swell. A spoil pile of sandy soil that scans at 60 loose yards represents about 53 bank yards at 14% swell. Stockpile Scan reports the pile as it is, with a ± range, and the conversion is one division afterwards; the accuracy guide covers what else can move the number.
Billed by the truckload: checking what was really removed
Homeowners meet swell when an excavation bill arrives in truckloads. Twenty loads at 12 yards is 240 loose yards, which is only about 190 bank yards of common earth, and the hole should be measured in bank yards. Public-works contracts have litigated exactly this. A Maryland contract appeals board decision records a specification that measured unclassified excavation by cross-sections taken before and after grading, while hauled unsuitable material was measured in the vehicle (MSBCA No. 2192). A 1955 California Public Utilities Commission decision explained why the two differ: excavated material occupies more space on the truck than in the bank, subject to a swell factor that varies with the material, its moisture and how it was loaded (CPUC Decision 51165).
The practical lessons are the same at any scale. Agree the unit before the first bucket: bank yards from the hole, or loose yards in the truck, with the swell factor written down. Keep the load tickets. Measure the hole, by tape or by scan, while it is open. And scan the spoil pile before it is hauled; a dated volume with photos is what settles a disagreement later. Our guides to sizing a debris pile and measuring a stockpile cover the measuring side, and the density table turns yards into the tons a scale ticket shows.
Frequently asked questions
What is a swell factor in excavation?
Swell is the percentage increase in volume when material is dug from its natural bank state and becomes loose. Sand and gravel swell about 10 to 18 percent, common earth about 25 percent and clay 20 to 35 percent. The load factor is the inverse: bank volume divided by loose volume.
How many loose cubic yards are in a bank cubic yard?
Between about 1.1 and 1.35, depending on the material. One bank yard of sand becomes roughly 1.1 to 1.18 loose yards; one bank yard of dry clay becomes about 1.26 loose yards. Divide a loose volume by that number to get back to bank yards.
Why is my dirt pile bigger than the hole it came from?
Digging mixes air into the soil. The same material that was dense in the ground now sits in a loose pile with 10 to 35 percent more volume. It will shrink again if it is placed and compacted, often to less than its original bank volume.
How can I verify how much dirt a contractor removed?
Measure the hole in bank yards, by tape or by scanning it, and compare it with the truckloads billed after converting those loose yards to bank with the material’s load factor. Keep the load tickets, agree the unit of measurement in writing before work starts, and measure the spoil pile before it is hauled away.
Measure your next pile with your iPhone
Stockpile Scan is free, with no ads, subscriptions or account. Scan the spoil pile before it is hauled and keep a dated volume, with photos, in loose yards you can convert.
Any iPhone with iOS 18 or later. LiDAR optional. Learn more about the app.
Related articles
Sources and further reading
- Propeller: Calculating shrink and swell
- SiteOne: Calculate bulk materials for landscape and hardscape
- Civils.ai: Soil bulking and swell factors
- Maryland State Board of Contract Appeals, No. 2192: excavation measured by cross-sections and in the vehicle
- California PUC Decision 51165 (1955): swell factor between bank and truck volume