Excavation Calculator — swell, haul and backfill
Bank, loose and compacted volumes for an excavation: how much you dig, how much you haul, and why the hole will not fill itself.
The hole, the truck and the backfill are three different volumes of the same dirt. Soil expands when you dig it and shrinks when you compact it, and both directions cost money.
Quick answer: a 40 × 30 × 4 ft hole, by soil
| Soil | Swell / shrink | Loose, to haul | 12 yd³ loads |
|---|---|---|---|
| Sand / gravel | 12 % / 12 % | 199.1 yd³ | 16.6 |
| Common earth | 25 % / 10 % | 222.2 yd³ | 18.5 |
| Clay | 30 % / 20 % | 231.1 yd³ | 19.3 |
| Blasted rock | 50 % / −30 % | 266.7 yd³ | 22.2 |
The hole is 177.8 yd³ in the bank. Swell and shrink are both measured against that bank volume, never one against the other; blasted rock compacts looser than it lay, so its shrink is negative.
| Bank volume (the hole) | — |
|---|---|
| Loose volume (on the truck) | — |
| Truck loads out | — |
| Backfill needed, compacted | — |
| Bank volume to supply that backfill | — |
| Net import / export | — |
The two percentages do not chain. Swell and shrinkage are both measured against bank volume, never against each other. Peurifoy’s Construction Planning, Equipment, and Methods says it flatly in section 2-4: both swell and shrinkage are calculated from the bank (or natural) condition. So the 125 loose yards that come out of a 100 yd³ hole in common earth do not then shrink 10% to 112.5. They compact to 90. The missing volume is a density: Table 2-5 puts common earth at 3,100 lb per bank yard against 3,450 compacted, and that ratio is the 0.90 the row above divides by.
Rock runs the other way. The same table gives blasted rock a shrinkage of −30% and a shrinkage factor of 1.30, footnoted compacted rock is less dense than is in-place rock. One bank yard of shot rock builds 1.3 compacted yards of embankment, so a rock cut ends in surplus. The blasted-rock preset above now carries that −30%, so it reports the export the table implies rather than an import that is not there. Choose Custom and enter −30 instead; the arithmetic takes the negative and prints an export.
Check the shrink figure before you price borrow. The swell presets match Table 2-5 exactly: 12, 25, 30, 50. The shrink column matches it too, clay 20% and sand and gravel 12%, after an earlier version of this page had 10% for both. On clay that more than doubles the import, 25 bank yards to fill a 100 yd³ void rather than 11.
What I check on a job
Where the money in earthwork hides. Before I let this page into an estimate, I find the line the money actually rides on. On most sites it is not the hole; it is the net import or export. The hole comes straight from measured dimensions, and swell never reaches the net line at all; swell only moves the haul and the load count. The net line is mostly the shrink factor working on the whole backfill, so a few points of error in shrink land there almost whole, on a line that is small to begin with. That makes shrink the figure I replace first with the geotechnical report's, and if the report gives none I say so in the estimate rather than let a planning range pass for a measurement. The other input I check is structure volume. It has to hold everything that will stay in the ground once the foundation is built; leave it at zero and the page prices backfill for a void the structure already fills.
Three volumes, one pile of dirt. Bank is soil in the ground, the hole
you measured. Loose is the same soil after digging, which occupies more space. That is
swell, and it is what you pay to haul. Compacted is soil placed and rolled back down, which
occupies less than bank. That is shrinkage, and it is why filling a hole takes more dirt than came
out of it.
Swell and shrinkage figures vary widely with soil, moisture and compaction effort. The values here
are ordinary planning ranges, not measurements of your site. On anything where the earthwork balance
matters, use the factors from your geotechnical report. Truck loads assume about 12 yd³ per load,
which changes with the truck and with local weight limits.
Worked example
Dig 40 × 30 ft, 4 ft deep in common earth: how many yards come out, and how many go on the truck?
- Bank volume = 40 × 30 × 4 = 4,800 ft³ = 177.8 yd³.
- Common earth swells 25%: 222.2 loose yards to haul.
- It also shrinks 10% compacted, so backfilling the same hole takes more than came out of it.
177.8 bank yards, 222.2 loose yards on trucks. The haul count and the backfill shortfall are both known before the machine arrives.
4 values on this page were driven in a browser and compared with independently derived figures on 2026-10-29 (2808 values across 228 calculators site-wide).
Questions
What is swell?
The volume increase when soil is dug out. Common earth swells about 25%: 100 bank yards become 125 loose yards on the truck.
Why does backfill come up short?
Because compacted soil is denser than bank soil — common earth shrinks about 10% — so the hole takes more than came out of it.
Do swell and shrinkage chain one after the other?
No. Both are measured against the bank volume (Peurifoy, section 2-4). A 100 yd³ hole in common earth gives 125 loose yards and compacts to 90, not to 112.5; Table 2-5's 3,100 lb per bank yard against 3,450 compacted is that 0.90.
Why does a rock cut end with surplus?
Because compacted rock is less dense than rock in place: Table 2-5 gives blasted rock a shrinkage of −30% and a factor of 1.30, so one bank yard builds 1.3 compacted yards of embankment. The blasted-rock preset carries the −30% and reports an export.