Soil changes volume three times during earthwork: in the ground (bank), in the truck (loose, swelled), and placed as fill (compacted, shrunk). Mixing up these states is one of the most common and costly errors in earthwork bidding and scheduling. This calculator converts cleanly between all three and estimates the number of truck loads to haul the loose material.
How it works
loose = bank × (1 + swell)
compacted = bank × (1 − shrinkage)
bank = loose / (1 + swell) = compacted / (1 − shrinkage)
truck loads = ceil(loose volume / truck capacity)Swell and shrinkage are independent soil properties: swell acts when you excavate, shrinkage acts when you compact. A single cubic yard of bank clay can swell to 1.25 yd³ loose in the truck and shrink back to only 0.88 yd³ compacted fill. Both transformations can be true simultaneously.
Worked example
100 yd³ bank excavation of common clay (25% swell, 12% shrinkage):
- Loose volume = 100 × 1.25 = 125 yd³ → ceil(125 / 20) = 7 truck loads (20 yd³ truck)
- Compacted fill = 100 × (1 − 0.12) = 88 yd³
Reverse question: You need 100 yd³ of compacted clay fill. How much bank material must you excavate?
- Bank needed = 100 / (1 − 0.12) = 100 / 0.88 = 113.6 yd³
If you excavate only 100 yd³ bank, you end up with only 88 yd³ of compacted fill — 12 yd³ short. This is the calculation that catches out many first-time earthwork estimates.
Typical swell and shrinkage factors
| Material | Swell % | Shrinkage % | Notes |
|---|---|---|---|
| Sandy soil | ~10–15% | ~5–8% | Low swell; compacts well |
| Common clay | ~20–30% | ~10–15% | Most variable; test before bidding |
| Gravel | ~10–12% | ~2–5% | Predictable; granular material |
| Topsoil | ~20–25% | ~10–12% | Organic content affects compaction |
| Soft rock / shale | ~30–40% | ~5–10% | Breaks down on excavation |
| Hard rock | ~50–80% | ~0% | Volume mostly increases; doesn’t shrink as fill |
These are typical mid-range values from earthwork references. Always use soil-specific test data for any real contract or bid — site-specific factors can differ substantially from these defaults.
Why these numbers matter for bidding
Under-counting loose volume means you order too few trucks and the job stalls mid-excavation waiting for more haulage.
Under-counting bank material needed for fill means you run out of cut material before achieving design grade and must import expensive borrow.
Over-counting compacted yield inflates the apparent fill coverage, causing grade deficits that require rework and import.
A consistent rule: always think in bank measure (the pay item on most contracts), convert to loose for haulage, and convert to compacted for fill placement — and do those conversions explicitly rather than eyeballing.