Swell Factor Calculator
Convert bank, loose and compacted volumes both ways from your own swell and shrinkage, or work out your swell factor and load factor from two things you measured. No soil factor is assumed.
The working
Loose volume = Bank volume × (1 + Swell)
Compacted volume = Bank volume × (1 − Shrinkage)
Loose volume
cubic yards
Waiting on you
Enter your swell for the loose volume, your shrinkage for the compacted volume, or both. The tool has no factor of its own: the published tables differ from one another, and the two that carry a variation note put ±33% on their factors.
Earth has three volumes on one job: in the ground (bank), dug and heaped (loose), and placed and rolled (compacted). Enter the swell and shrinkage from your geotechnical report or your own measurements and the tool converts any one volume to the other two, with the working shown. If you have measured two densities, two weights of the same container or two volumes of the same material, the second mode gives the swell, the load factor and the shrinkage they imply. Until you enter a factor the tool returns no converted volume, because any figure it produced would be somebody else’s guess. For truck loads, take the loose volume to the dirt hauling calculator with your own truck capacity.
How this calculator works
Only your inputs and exact unit conversions. Where a figure comes from anywhere else, it is recorded below with its source.
- Formula version
- 1.0.0
- Last reviewed
- 2026-09-30
- External data
- 3 sources
- Category
- Earthwork
What this calculates
One thing in two directions. The first mode takes a volume in one state and the swell and shrinkage you enter, and returns the volume in the other states. The second mode takes two measurements of the same material and returns the swell, the load factor and, if you have a compacted figure, the shrinkage. Neither mode supplies a factor of its own.
The three volumes and the formulas
Bank volume is the material in the ground, undisturbed, measured in place. Loose volume is the same material once dug and heaped, in a truck or a stockpile. Compacted volume is the same material placed and rolled. For the same material on the same moisture basis the weight does not change; only the room it takes up does.
Loose volume = Bank volume × (1 + Swell), and back: Bank volume = Loose volume ÷ (1 + Swell). Compacted volume = Bank volume × (1 − Shrinkage), and back: Bank volume = Compacted volume ÷ (1 − Shrinkage). Swell and shrinkage are percentages of the bank volume. To go between loose and compacted the tool goes through bank: Loose per compacted = (1 + Swell) ÷ (1 − Shrinkage). A factor is never applied to a volume that is already in the state it describes.
Swell, swell factor and load factor
Swell is a percentage: 25% swell means 100 bank cubic yards become 125 loose. The load factor is the same ratio the other way up: Load factor = 1 ÷ (1 + Swell) = Bank volume ÷ Loose volume, so 25% swell is a load factor of 0.8, and a loose volume times 0.8 is the bank volume. The reference table below is that formula worked at fourteen swell values.
Sources do not use the words alike. Caterpillar’s article on swell and load factors defines the load factor in words as loose over bank, while every load factor in its own table is bank over loose; this page follows the table. Some estimating software calls 1.25 the swell factor where others call 25% the swell factor, so a swell under 3% in the tool draws a note asking whether a ratio was entered. And “compaction factor” is a shrinkage in some places and the compacted-to-loose ratio in others. Check which one your source means before you type it in.
Shrinkage or expansion of the fill: which one is your figure?
Two ways of writing compaction are in use, and they give different numbers for the same soil. Shrinkage is measured on the bank volume: Compacted = Bank × (1 − Shrinkage). Wisconsin DOT’s method, which it calls “expand the fill”, is measured on the compacted volume: Bank = Compacted × (1 + Expansion). A shrinkage of 10% is a fill expansion of 11.11%: 1 ÷ 0.9 − 1. To choose which your source uses, open “Add detail” and set “How your compaction figure is defined”; the working says which was applied. The WisDOT report defines shrinkage from the densities as 1 − (bank density ÷ compacted density), and the expansion of the fill as compacted density ÷ bank density − 1.
Finding your own swell from measurements
Swell comes from a pair of measurements of the same material. From densities (weight per unit volume): Swell = (Bank density ÷ Loose density − 1) × 100. Because the weight is the same in every state, the volume ratio is the density ratio upside down: Loose volume ÷ Bank volume = Bank density ÷ Loose density. The weights of two samples of the same volume, one of undisturbed material and one of the same material dug and loose, give that ratio directly. Two volumes give it without any weighing: Swell = (Loose volume ÷ Bank volume − 1) × 100. Caterpillar’s article gives the same relation in words: it takes 30 percent more volume to hold the same weight after excavation if the swell is 30 percent. The Federal Highway Administration’s earthwork exhibit prints in-situ and loose densities beside a percent swell footnoted “Based on average in-situ densities”, and in most of its rows the printed swell equals in-situ density ÷ loose density − 1 (57 of the 64 rows that print all three figures, to within a point).
The bank figure has to come from the material in the ground: an in-ground sample of known volume that was weighed, a volume you measured in place, or a bank density that your geotechnical report or another source states. Material shovelled into a container is already loose, so it cannot give a bank weight or density, and using it would show a swell near zero.
Shrinkage is the same with the compacted figure: 1 − Bank density ÷ Compacted density, or 1 − Compacted volume ÷ Bank volume. All the figures in a pair must be for the same material on the same moisture basis, all as found or all dry, and the tool cannot check that.
Why there is no list of soils
Swell and shrinkage move with the material, its moisture, how it is dug, the compaction specified and the size of the job. The published tables differ from one another: the WisDOT report gathers several. Of the tables read for this page, two carry a variation note, and both put ±33% on their factors: the note under the report’s table of Church’s (1981) factors says they are subject to an average ±33 percent variation, and the FHWA exhibit’s footnote says “Factors subject to ±33% variation.” A dropdown that fills in “clay: 30%” would put one table’s guess on the page with the authority of a lookup. So the factor fields open blank, the tool shows what it is waiting for, and a preset soil is not an option.
Where a real factor comes from: the geotechnical report for the site; your hauler’s or excavator’s records for the same material from the same area (FHWA says the design should consider actual field factors for like material used on adjoining projects, when available); or a measurement of your own, using the second mode. One truck of a known bank volume gives a rough check on a figure, not a factor for the whole job.
Trucks, weight and price
A truck body or a stockpile holds loose volume, but a load also depends on the truck’s own capacity and on the weight limit, which are yours to enter. The dirt hauling calculator takes a loose volume and your truck and counts the loads. This tool stops at the volume, so the two are not duplicated. It does not convert to tons or price anything.
A stockpile measured loose, converted back to bank and compacted
The swell and shrinkage below are made up for the arithmetic. They are not Calcumetryx figures and not a statement about any soil. Put your own in and the working is identical.
- Loose volume (measured)
- 150 cu yd
- Swell (illustrative)
- 25%
- Shrinkage (illustrative)
- 10%
- 01Loose per bank = 1 + Swell= 1 + 25%= 1.25
- 02Bank volume = Loose volume ÷ (1 + Swell)= 150 ÷ 1.25= 120 cu yd
- 03Compacted per bank = 1 − Shrinkage= 1 − 10%= 0.9
- 04Compacted volume = Bank volume × (1 − Shrinkage)= 120 × 0.9= 108 cu yd
- 05Load factor = 1 ÷ (1 + Swell)= 1 ÷ 1.25= 0.8
120 bank, 108 compacted
Swell and load factor: the arithmetic
Every row is computed from the formula on this page, load factor = 1 ÷ (1 + swell). It is a conversion between two ways of writing one ratio, not a property of any soil: which swell applies to your material is your figure to supply.
| Swell | Loose per 1 bank | Load factor | Bank per 100 loose |
|---|---|---|---|
| 5% | 1.05 | 0.952 | 95.2 |
| 10% | 1.10 | 0.909 | 90.9 |
| 15% | 1.15 | 0.870 | 87.0 |
| 20% | 1.20 | 0.833 | 83.3 |
| 25% | 1.25 | 0.800 | 80.0 |
| 30% | 1.30 | 0.769 | 76.9 |
| 35% | 1.35 | 0.741 | 74.1 |
| 40% | 1.40 | 0.714 | 71.4 |
| 45% | 1.45 | 0.690 | 69.0 |
| 50% | 1.50 | 0.667 | 66.7 |
| 55% | 1.55 | 0.645 | 64.5 |
| 60% | 1.60 | 0.625 | 62.5 |
| 65% | 1.65 | 0.606 | 60.6 |
| 70% | 1.70 | 0.588 | 58.8 |
Load factor is bank volume ÷ loose volume. Multiply a loose volume by it to get the bank volume.
What it assumes
- 01The swell, shrinkage or expansion you enter is a percentage that applies to the whole quantity, for one material handled one way.
- 02Swell and shrinkage are percentages of the bank volume; fill expansion is a percentage of the compacted volume. You choose which one your source means.
- 03The volume you enter is in the state you chose: bank, loose or compacted.
- 04Measurements you enter to find a factor are of the same material on the same moisture basis: all as found, or all dry.
- 05A bank measurement is of the material in the ground (an in-ground sample, a volume measured in place, or a bank density from a report), never of material shovelled into a container, which is already loose.
- 06Cubic yards, cubic feet and cubic metres are exact conversions (1 cu yd = 27 cu ft = 0.9144³ m³).
What it does not do
- It does not know any material’s swell or shrinkage and applies only what you enter or measure. That is why there is no list of soils to pick from.
- It gives a volume, not truck loads, weight or price. Use the dirt hauling calculator with your own truck capacity, and the cubic yards to tons calculator with your own density.
- It is not a compaction test. It does not compare a density with a Proctor value or say whether a fill passes.
- One swell and one shrinkage apply to the whole quantity. Layered soils, or soil mixed with rock, need a separate run for each.
- A factor from a design manual may include more than the soil’s volume change: FHWA says shrink generally includes the slight waste in transporting material from cut to fill and the loss of material that escapes beyond the toe of slopes, and that slightly overbuilt embankments and settlement of the ground under an embankment contribute to an apparent shrink. The tool applies whatever factor you give it as a pure volume ratio.
- It does not adjust for over-excavation, settlement of a stockpile in transit or moisture changing between the pit and the truck.
Common questions.
- What is a swell factor?
- The amount by which earth grows when it is dug. Digging breaks the material into particles that do not fit together, and the voids between them add volume, so a bank cubic yard becomes more than a cubic yard loose. It is usually written as a percentage of the bank volume: 25% swell means 100 bank cubic yards become 125 loose. Some software writes the same thing as a ratio, 1.25, and calls that the swell factor. This calculator asks for the percentage, so enter 25.
- How do I calculate the swell factor?
- From two measurements of the same material: its density in the ground and its density loose. If a cubic foot of it weighs 100 lb in the ground and 80 lb loose, the swell is 100 ÷ 80 − 1 = 25%. Those figures are for the arithmetic only, and to try them choose lb/cu ft as the unit beside each. The bank figure has to come from the material in the ground: an in-ground sample of known volume, or a bank density that your geotechnical report or another source states. Material shovelled into a container is already loose. You can also use volumes: if 10 cubic yards in the ground made 12.5 cubic yards in the truck, the swell is 12.5 ÷ 10 − 1 = 25%. Choose “Find my swell factor” above and enter your own figures; it shows every step.
- What is the load factor, and how does it relate to the swell?
- The load factor is 1 ÷ (1 + swell), the bank volume per unit of loose volume. With 25% swell it is 0.8, so a 10-yard truck of loose material holds 8 bank yards of excavation. It is the same information as the swell, written the way you use it to go from a truck count back to the survey.
- How do I convert bank cubic yards to loose cubic yards?
- Multiply by one plus the swell. With 25% swell, 100 bank cubic yards × 1.25 = 125 loose. The calculator does this when the volume is set to bank and you enter your swell. The 25% is an example: take yours from your geotechnical report, your hauler’s records or a measurement.
- How do I convert loose cubic yards to bank cubic yards?
- Divide by one plus the swell, or multiply by the load factor. With 25% swell, 150 loose cubic yards ÷ 1.25 = 120 bank. Do not multiply a loose volume by the swell a second time: the swell is measured on the bank volume, so converting back divides.
- What is the difference between swell and shrinkage?
- Swell takes bank to loose, and it is what a truck carries. Shrinkage takes bank to compacted, and it is what a fill consumes. FHWA’s earthwork guidance says excavated common material typically shrinks below the excavated volume when it is compacted into the fill, while excavated solid rock placed in a fill typically occupies a larger volume, so for rock the shrinkage comes out negative. They are two separate measurements for the same soil. Shrinkage is not the swell with the sign changed, and neither can be worked out from the other.
- Shrinkage or expansion of the fill: which do I enter?
- Whichever your source defines. The Wisconsin DOT report says the terminology and procedures vary among agencies and sources. A shrinkage factor, a percentage of the bank volume, is commonly employed, but some DOTs prefer “shrink the cut” and others “expand the fill”. Wisconsin DOT uses “expand the fill”, a percentage of the compacted volume, and a 10% shrinkage is an 11.11% expansion of the fill. To match your source, open “Add detail” and set “How your compaction figure is defined”; the working states which one was applied.
- What swell factor should I use for clay, sand or gravel?
- This calculator does not give one, and any figure it gave would be a guess with a table’s authority. The published tables differ from one another, and the two that carry a variation note put ±33% on their factors: the note under the WisDOT report’s table of Church’s (1981) factors says an average ±33 percent, and the FHWA exhibit’s footnote says ±33%. The factor depends on your material, its moisture and how it is dug. See the guide on soil compaction, shrinkage and swell for what the FHWA, DOT and textbook tables say side by side, and use your geotechnical report or a measurement of your own.
- Can it convert compacted volume straight to loose volume?
- Yes, with both factors entered. It goes through the bank volume: compacted ÷ (1 − shrinkage) gives bank, and bank × (1 + swell) gives loose. It also shows the one-step ratio, loose per compacted = (1 + swell) ÷ (1 − shrinkage), which is the number to multiply a compacted fill quantity by to know how much loose material to order or haul.
- Does it count truck loads?
- No. A load depends on your own truck’s capacity and weight limit, and the dirt hauling calculator already counts loads from a loose volume. Take the loose volume from here into that tool with your truck capacity.
- Does the tool assume any factors?
- None. The swell, shrinkage and expansion fields open blank, and the tool waits for them instead of filling one in. The volume opens at 100 cubic yards as a starting value for you to overwrite. Every other number it applies is one you typed or measured, plus exact unit conversions.
Behind the numbers
The methods and definitions this calculator applies, explained in full and with their sources.
Where people go next
Ordered by what usually comes next in the same job, not by keyword.