Calculator

Excavation Spoil Calculator

Soil takes up more room once it's out of the ground than it did in it. The compacted, undisturbed dirt in a hole is bank measure; the same dirt piled beside the hole, with air worked into it by the digging, is loose measure — and depending on the soil type, that loose pile can be a quarter to more than half again the volume of the hole it came from. Order spoil removal against the hole's own volume and the truck runs out of room before the pile does.

This calculator keeps hole volume, pile volume, and what actually needs hauling away as three separate figures, because they answer three different questions: how big a hole are you digging, how big a pile does that make, and — once whatever's staying in the ground (a footing, a slab, a tank, or a permanent pond) is accounted for — how much of that pile is genuinely leaving the site. A job where most of the spoil goes back in as backfill and a job where none of it does can start from the same hole size and end with very different truckloads.

Calculate your quantity

Excavation length (ft)

Excavation width (ft)

Excavation depth (ft)

Swell factor

Compaction shrink (%)

Volume the structure fills

cubic yards of footing, slab or tank going into the hole

Truck capacity

cubic yards

Excavated volume (bank)

35.56 cu yd

Spoil pile (loose)

44.44 cu yd

Hole volume: 960 cu ft
Swell: 8.89 cu yd
Backfill available (loose): 44.44 cu yd
To haul away: 0 cu yd
Truckloads: -0 loads
Approximate pile height: 10.5 ft
Compacted backfill shrink allowance: 10 %

A 35.56 cu yd hole makes a 44.44 cu yd pile — 25% more than came out of the ground. Ordering removal against the hole's volume is how a one-truck job becomes a two-truck job.
Backfill compacts again as it goes back in, so allow another 10% on any imported fill you are compacting in lifts.

Shopping summary

• No spoil removal needed

This is an estimate — confirm structural work with a professional.

How this calculation works

Hole volume comes straight from length, width and depth, converted to cubic yards. The loose pile is that bank volume increased by a swell percentage that varies by soil type — sand and gravel swell the least because their particles were already loosely packed, dense clay swells more because compacted clay is dramatically denser in the ground than once it's broken up, and blasted rock swells the most of anything this page handles.

Backfill available is bank volume minus whatever's staying in the hole permanently — enter that as the structure volume, whether it's a footing, a slab, a buried tank, or a pond that will hold water rather than dirt. What's left after that subtraction is backfill, and it swells the same way the rest of the pile does once it's dug out and set aside before being put back. Whatever loose volume the pile has beyond that backfill amount is what actually gets hauled away and billed by the truckload.

Swell only applies once — soil that's already been dug and is being moved a second time doesn't swell again, it's already at loose measure.
Backfill itself compacts back down once it's replaced and tamped, which is a separate shrink allowance from the swell that happened when it came out — the two percentages describe opposite directions of the same soil's volume change.
Setting the structure volume equal to or greater than the hole's own bank volume tells the calculator nothing comes back as backfill — the correct entry for a hole, like a pond, that's meant to stay open rather than be filled back in.
Truckloads round up to whole trips, since a truck can't make a fractional delivery — a haul-away volume just over a round truck capacity still costs a full extra trip.

The formula

looseCuyd = bankCuyd x (1 + swellPct/100); haulAway = looseCuyd − max(0, bankCuyd − structureCuyd) x (1 + swellPct/100)

bankCuyd: The hole's own volume, in cubic yards, as it sits undisturbed in the ground — length times width times depth, converted from cubic feet. This is the excavation size a contractor or equipment operator is typically quoted against.
swellPct: How much a specific soil or rock type's volume increases once dug and loosened — roughly 12% for sand and gravel up through 60% for blasted rock. The single biggest lever in how much bigger the pile is than the hole.
structureCuyd: The volume of whatever stays in the hole permanently and never returns as backfill — a footing, a slab, a tank, or (entered as the full hole volume) a pond meant to hold water rather than be filled back in.
backfillAvailable: Bank volume minus structure volume, then increased by the same swell percentage — the loose soil genuinely available to go back into the hole around whatever's staying there, floored at zero if the structure takes up the entire hole.
haulAway: Loose pile volume minus backfill available — the soil that has nowhere to go back to and needs to leave the site, which is what a spoil-removal truckload count is actually based on.
pileHeight: A rough visual check assuming the loose spoil forms a roughly conical pile — useful for judging whether a pile will physically fit in the space beside the hole before digging starts, not a precision figure.

Where these numbers come from

Swell factors from about 12% (sand/gravel) to 60% (blasted rock): Commonly cited ranges in construction-estimating references for how much different soil and rock types expand once excavated. Actual swell varies with moisture content and the specific material, so treat these as planning figures — a wetter or more cohesive soil within the same general category can swell more than the low end of its range.
10% default compaction shrink on backfill: A commonly cited approximate figure for how much loose backfill volume is lost once it's replaced and compacted in lifts — actual shrink depends heavily on compaction effort and the specific material, and can run higher for engineered fill compacted to a specified density.
10 cu yd default truck capacity: A common single-axle dump truck box capacity used here as a planning default. A tandem-axle truck or a larger tri-axle can run meaningfully higher — enter your specific hauler's quoted box capacity once you have a truck booked, rather than relying on this default for a firm trip count.

Worked examples

A basement addition excavation, most of the spoil returning as backfill

Inputs
Excavation length	20 ft
Excavation width	12 ft
Excavation depth	4 ft
Swell factor	Common earth (25%)
Compaction shrink	10 %
Volume the structure fills	20
Truck capacity	10

Result
Excavated volume (bank)	35.56 cu yd
Spoil pile (loose)	44.44 cu yd
Hole volume	960 cu ft
Swell	8.89 cu yd
Backfill available (loose)	19.44 cu yd
To haul away	25 cu yd
Truckloads	3 loads
Approximate pile height	10.5 ft
Compacted backfill shrink allowance	10 %

35.56 cu yd of bank-measure hole becomes a 44.44 cu yd loose pile at common earth's 25% swell — nearly 9 extra cubic yards that weren't visible in the hole itself. With a 20 cu yd slab-and-footing structure staying in the ground, 15.56 cu yd of bank material is available to come back as backfill, which swells to 19.44 cu yd loose.

The difference between the 44.44 cu yd pile and the 19.44 cu yd that goes back in is 25 cu yd that genuinely has to leave the site — 3 truckloads at a 10 cu yd capacity, not the roughly 2 you'd expect from the raw hole size alone. Ordering removal against bank volume here would have come up a full truckload short.

A pond excavation in dense clay, where nothing comes back as backfill

Inputs
Excavation length	10 ft
Excavation width	8 ft
Excavation depth	3 ft
Swell factor	Dense clay (40%)
Compaction shrink	10 %
Volume the structure fills	9
Truck capacity	12

Result
Excavated volume (bank)	8.89 cu yd
Spoil pile (loose)	12.44 cu yd
Hole volume	240 cu ft
Swell	3.56 cu yd
Backfill available (loose)	0 cu yd
To haul away	12.44 cu yd
Truckloads	2 loads
Approximate pile height	6.8 ft
Compacted backfill shrink allowance	10 %

Entering the structure volume equal to the full bank volume here tells the calculator this hole isn't getting backfilled at all — it's a pond, and water, not returned soil, is what fills the space once the liner goes in. Backfill available comes out to zero, so the entire 12.44 cu yd loose pile — the full swelled volume of a much smaller 8.89 cu yd hole — has to leave the site.

This is the opposite case from the basement addition above: a smaller hole, but because nothing returns as backfill, a higher share of the pile ends up on a truck. Two loads at 12 cu yd capacity cover it here, against three loads for the larger but mostly-backfilled basement hole — proof that hole size alone doesn't predict truckload count nearly as well as how much of the pile actually leaves.

Common mistakes

Ordering spoil removal against the hole's bank volume instead of the swelled loose volume. This is the single most common way a one-truck estimate turns into a two-truck job on site.
Forgetting that a structure staying in the hole reduces available backfill, not the pile size. The pile is still the full swelled bank volume; what changes is how much of it has somewhere to go back to.
Entering zero for structure volume on a hole that isn't actually getting fully backfilled, like a pond or a below-grade patio drain field. That tells the calculator all the spoil comes back, badly understating truckloads for a hole meant to stay open.
Applying swell twice — once when the material is dug, and again when it's later moved from a temporary pile to a truck. Swell happens once, at the point the soil is disturbed; moving already-loose material a second time doesn't swell it further.
Ignoring compaction shrink when estimating how much imported fill a project needs on top of its own backfill. Fill compacted in lifts loses volume as it's compacted, so a project relying partly on imported fill needs to order more than the bare volume gap suggests.

Shopping summary

Book spoil removal by the truckload figure this page reports, not by the hole's bank volume — that's the number a hauler actually bills against, and it already accounts for both swell and whatever's coming back as backfill.

If the hole is for a footing or slab rather than staying open, the concrete slab calculator or deck footing calculator sizes what's actually going into the structure volume field here, and if it's for a pond, the pond liner calculator sizes the liner the finished hole needs once digging is done.

FAQ

Why does the pond example need fewer trucks in total, even though a higher share of its pile leaves the site?

Because its hole is much smaller to begin with — 8.89 cu yd bank measure against the basement example's 35.56 cu yd. A smaller hole with a higher backfill-return rate can still need more trucks than a smaller hole with none, or fewer than a bigger hole with some, depending on exactly how the numbers land; hole size and haul-away share both matter, and neither one alone predicts the truckload count.

What swell factor should I use if I'm not sure what kind of soil I have?

Common earth's roughly 25% figure is a reasonable middle-of-the-road planning default for typical topsoil and subsoil mixes. If you've dug on the site before and know it runs heavier in clay or looser in sand and gravel, lean toward that category's figure instead — being wrong on this input mainly affects how conservatively you estimate truckloads, not whether the hole itself gets dug correctly.

Does the pile height figure account for the pile being compacted by equipment driving over it?

No — it assumes a freshly dumped, uncompacted loose pile in a roughly conical shape, which is the more conservative (taller, more space-hungry) assumption. A pile repeatedly driven over by equipment will settle somewhat and take up less height than this figure suggests, but shouldn't be relied on to fit in a tighter space than the uncompacted estimate implies.

How do I handle a job where different parts of the hole have different soil types?

Run this calculator once per soil layer if the difference is significant — a hole that's mostly common earth but hits a band of clay partway down will genuinely produce more loose volume from that clay layer than the same depth of earth would. Splitting the excavation by layer and adding the results is more accurate than picking one swell factor for the whole hole.

Why is compaction shrink a separate figure from swell, when they seem like opposites?

Because they describe the same soil at different points in its journey and don't exactly cancel out. Swell happens once, when the soil is first disturbed; shrink happens separately when it's later compacted back into place, and the two percentages aren't necessarily equal — soil rarely returns to exactly its original bank density once it's been dug, moved, and replaced.

Where to go next

The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.