Soil Swell & Shrink Calculator
One volume of dirt is three different numbers depending on where it sits: bank (undisturbed in the ground — what plans and pay items usually reference), loose (broken up on a truck), and compacted (placed and rolled). Enter a bank volume, pick a soil class, and get the loose and compacted equivalents at typical swell and shrink factors — shown with their ranges, because these are planning figures, not physical constants. Free, no login.
Soil
Common earth / loam: +25% swell, −10% shrink (typical).
Equivalent Volumes
Bank → loose × (1 + swell); bank → compacted × (1 − shrink). Common earth / loam: swell 25% (typ 15–30%), shrink 10% (typ 5–15%) — factors vary widely; confirm with a geotech.
How this calculator works
Both factors are referenced to bank volume — swell measures the gain from bank to loose, shrink the loss from bank to compacted:
loose = bank × (1 + swell%) · compacted = bank × (1 − shrink%)
The conversions themselves are exact once the factors are chosen — the factors are the uncertain part. Soil swell and shrink are empirical, ranged properties that move with material, gradation, and moisture: typical published ranges run 5–18% swell for sand/gravel, 15–30% for common earth, 20–40% for clay, and 40–65% for blasted rock. The presets are mid-range planning defaults. For pay quantities, haul contracts, or borrow budgets, confirm the factors with a geotech or a field test on the actual material.
Worked example
100 bank yd³ of common earth (25% swell, 10% shrink defaults):
- Loose: 100 × 1.25 = 125 yd³ on trucks — 25% more loads than the bank quantity suggests.
- Compacted: 100 × 0.90 = 90 yd³ in place — the same cut fills 10% less hole than it left.
- The spread is the point: one bank quantity becomes 125 loose and 90 compacted, so a “100-yard” line item means three different truck and fill realities.
Enter 100 yd³ with common earth above to reproduce it, then switch to blasted rock: 150 loose, 100 compacted — rock never shrinks below bank.
Reference: swell and shrink by soil class
The calculator’s factor set with typical ranges, and what 100 bank yd³ becomes in each state at the defaults — computed by the same engine. Ranges are the honest answer: confirm with a geotech for a specific site or borrow source.
| Soil class | Swell (typ range) | Shrink (typ range) | 100 bank → loose | 100 bank → compacted |
|---|---|---|---|---|
| Sand / gravel | 12% (5–18%) | 12% (8–15%) | 112 yd³ | 88 yd³ |
| Common earth / loam | 25% (15–30%) | 10% (5–15%) | 125 yd³ | 90 yd³ |
| Clay | 30% (20–40%) | 10% (5–20%) | 130 yd³ | 90 yd³ |
| Rock (blasted) | 50% (40–65%) | 0% (0–5%) | 150 yd³ | 100 yd³ |
Frequently asked questions
What do bank, loose, and compacted cubic yards mean?
Bank cubic yards (BCY) is soil measured in place, undisturbed — the state you dig, and usually the state pay quantities reference. Loose cubic yards (LCY) is the same material after excavation, bulked up with air voids — the state you load and haul. Compacted cubic yards (CCY) is the material after placement and compaction — for most soils, less than the original bank volume. This calculator converts a bank volume into its loose and compacted equivalents.
What are typical swell and shrink percentages by soil type?
This calculator’s planning defaults are: sand/gravel 12% swell and 12% shrink, common earth 25% and 10%, clay 30% and 10%, blasted rock 50% swell and 0% shrink. Real values are ranges — roughly 5–18% swell for granular soils, 15–30% for common earth, 20–40% for clay, 40–65% for blasted rock, with shrink anywhere from about 5% to 20% depending on material, moisture, and compactive effort. Treat the presets as starting points; the geotech report or a field test on the actual soil governs.
What is a load factor and how does it relate to swell?
Load factor converts loose volume back to bank: LF = 1 ÷ (1 + swell), so a soil with 25% swell has a load factor of 0.80 — a 20-yard loose truck load is only 16 bank yards. Production rates and haul pay quantities are often stated in bank yards while everything you actually load and haul is loose, and the load factor is how you reconcile the two. This calculator runs the same conversion in the other direction, bank to loose.
If I dig a hole and put the same dirt back, why doesn’t it fit?
Both classic outcomes are real, and they are two ends of the same physics. Fresh off the pile the soil is loose and swelled, so a full backfill leaves a mound; but if you compact each lift to spec, most soils shrink below their original bank volume — 100 bank yards of common earth compacts back to roughly 85–95 yards, and the hole comes up short without import. Uncompacted backfill splits the difference the bad way: the mound settles over time, which is why poorly compacted trenches sink. Rock is the exception — it never compacts back below its bank volume.
Which volume do I use for hauling, and which for buying fill?
Haul off in loose yards — that is what occupies the truck. Buy fill against the compacted yardage the plans require, converted to a loose order quantity: compacted × (1 + swell) ÷ (1 − shrink). Digging and pay quantities are usually bank. Mixing these states — pricing haul by bank yards, or ordering fill one-for-one against compacted yards — is where earthwork estimates most often go wrong.
Method: bank → loose × (1 + swell) and bank → compacted × (1 − shrink), both factors referenced to bank (in-place) volume. The arithmetic is exact; the factors are typical planning ranges (typ 10–40% by soil class for most soils; blasted rock swells 40–65% and carries 0% shrink because placed rock does not compact below bank volume). Moisture, gradation, and the compaction spec all move the real numbers — the geotech report or a field test on the actual material governs pay quantities and haul contracts.
Pair with the swell & shrink factor chart for the full material list and load-factor math, the material weight chart to turn yards into tons, or the Excavation Volume Calculator and Compaction Calculator that put these conversions to work.