Bank, loose and compacted are three different volumes of the same dirt
Earthwork is the one trade where the same material has three legitimate volumes and using the wrong one costs real money. Bank volume is the material sitting undisturbed in the ground, and it is what the hole measures. Loose volume is that same material after a bucket has broken it up, when the particles no longer nest together and there is air between them. Compacted volume is what you get after it has been placed in lifts and rolled, which is denser than loose and usually denser than bank.
The expansion from bank to loose is called swell, and it is the reason an excavation estimate that only computes length times width times depth under-orders trucking. Dig 89 bank yards of average material with 25 percent swell and 111 loose yards come out. At 12 loose yards a truck that is 10 loads rather than the 8 you budgeted, which on most jobs is a bigger line item than the digging.
The reduction from bank to compacted is called shrink, and it works the other way. If you are reusing spoil as engineered fill, a bank yard does not build a bank yard of fill. It builds somewhat less, because the compaction effort drives out voids the material had in the ground. Both factors are inputs here rather than fixed numbers, because they are properties of the specific material at its specific moisture content, and the only person who can give you a defensible figure is whoever is moving it.
Typical ranges, and why nobody will give you an exact one
| Material | Swell, bank to loose | Shrink, bank to compacted |
|---|---|---|
| Sand and gravel, dry | Low end of the range, near 10-15% | Small, sometimes near zero |
| Common earth, loam | Middle, around 20-25% | Around 10-15% |
| Clay, dense or wet | High, 25-35% and up | Can be large and moisture-dependent |
| Blasted rock | Far higher, often 40-60% | Negative — rock fill occupies more than the ledge did |
These are orientation, not specifications. Moisture content swings the numbers hard, and the same clay dug in August and in March behaves differently enough that an experienced operator will quote you different figures. If the job is large enough that the difference matters, the material gets tested rather than guessed.
Working room is not optional and it is not in the drawing
Plans dimension the structure, not the hole. If a foundation wall has to be formed, stripped, damp-proofed and drained from the outside, somebody has to stand there. That working room is added to every horizontal side, so a two-foot allowance on a 20 by 30 footprint is not 20 by 32 — it is 24 by 34, and the volume goes up by nearly a third before the depth is even considered. This is the single most common reason a dig quantity comes in over estimate.
The same applies at the top when the walls are sloped back rather than shored. A sloped excavation removes a great deal more material than a vertical-sided one, and the extra grows with the square of the depth. This calculator has no slope input on purpose. Slope angles are a protective-system decision made by a competent person on the ground looking at the actual soil, and putting a number field on it would suggest otherwise.
Where this stops being arithmetic
Volume is the cheap half of earthwork. What the number cannot tell you is whether the soil at the bottom will carry what you intend to put on it, whether the water table is where you think, whether the spoil is clean enough to be legally placed somewhere else, or whether the excavation is stable for the hours a crew will spend in it. Those are site questions with site answers.
Two things are worth stating plainly because people die of them every year. First, call the free national utility locate service before you break ground — every state has one, and hitting a gas or electric line is not an inconvenience. Second, excavation walls collapse without warning, and a cubic yard of the soil in your hole weighs on the order of a small car. That is why trench protection and competent-person oversight are required work rather than good practice. Once the volume is settled, take the cut and fill calculator to see whether the site balances, and the concrete footing calculator for what goes back in the hole.
Questions people ask
Why does the truck hold fewer yards than the hole produced?
It does not — the hole produced more yards than you measured. A truck box is measured in loose cubic yards, because loose material is the only kind that ever goes in a truck. The hole is measured in bank cubic yards. With 25 percent swell, 89 bank yards is 111 loose yards, so a 12 yard truck makes 10 trips rather than 8. The mistake is comparing a bank number against a loose capacity. Ask the hauler which unit their price is in before you compare quotes, because both are used and the difference is a quarter of the job.
How do I know what swell factor to use?
You ask the person doing the work, and if the job is large you have the material tested. Swell depends on the material, its density in the ground, and above all its moisture content, and those vary within a single site. The ranges in the guide above are for orienting a budget, not for writing into a contract. If you have to pick blind for a small residential dig in ordinary soil, something in the low twenties is the usual working assumption, and you carry the risk that clay or wet conditions push it higher. Estimating high on swell costs you an unused truck slot. Estimating low leaves material on the ground with nowhere to go.
Can I use the spoil from the hole as backfill?
Sometimes, and the volume works against you either way. Structurally, whether excavated material is acceptable as engineered fill depends on what it is — organic topsoil and soft clay generally are not, and material placed against a foundation or under anything that will be loaded is usually specified rather than assumed. Numerically, a bank yard of spoil places as less than a bank yard of compacted fill because of shrink, so reusing everything still leaves you short. Set the reuse percentage here and the calculator shows both the compacted volume you get and the surplus that still has to leave.
Does the calculator account for sloping the excavation walls back?
No, deliberately. A sloped or benched excavation removes substantially more material than a vertical-sided one, and the additional volume grows with the square of the depth, so it is not a small correction. But the slope angle is not an arithmetic choice. It is a protective-system decision that belongs to a competent person evaluating the actual soil, water and surcharge conditions on the day, and it changes as those conditions change. Putting a slope field here would imply the geometry can be picked from a dropdown. If your excavation will be sloped, get the angle from the person responsible for the protective system and add the extra footprint using the working-room field.
How much does a cubic yard of dirt weigh?
For in-place soil, commonly somewhere between about 2,300 and 3,200 lb depending on material and moisture, which is why the density is an input here rather than a constant. Set it and the calculator converts. The figure matters twice over. It decides whether a truck fills up by volume or hits its legal weight limit first, which on wet clay it usually does. And it is the reason excavation collapse is fatal rather than inconvenient: that is roughly the mass of a small car arriving on someone with no warning and no way to move.