Digging seems like the simple part of a project until you have to move the spoil — and there is always more of it than the hole suggests, because soil expands when you dig it up. This calculator estimates the in-ground volume from your dig dimensions and then the loose volume you actually have to haul, so disposal and trucking are sized correctly.
How excavation volume is calculated
Cubic yards = cubic feet ÷ 27
Loose volume = in-ground × swell factor (~1.25)
The swell factor is the part people miss. Compacted, undisturbed soil takes up less space than the same soil once it is dug and loosened. A 25% swell is typical, which means a tidy hole produces a noticeably larger pile to remove.
Measuring the dig
- Footings and trenches: length × width × depth of the trench.
- Pads and basements: the full footprint × depth, plus extra width for working room and sloped sides.
- Sloped or stepped sites: break the dig into sections of roughly even depth and add them.
Swell factors by soil type
| Soil | Approx swell |
|---|---|
| Sand / gravel | 10–15% |
| Common loam | 20–25% |
| Clay | 25–40% |
| Rock | up to 50%+ |
A worked example
A 20×12 ft area dug 1 ft deep, common soil with 25% swell:
- In-ground = 20 × 12 × 1 = 240 cu ft = 8.9 yd³
- Loose volume = 8.9 × 1.25 = 11.1 cubic yards to haul
- That is about one full dump-truck load
Disposal, reuse and cost
Decide early what happens to the spoil. Clean topsoil can be reused on site for grading or beds — the related topsoil calculator helps place it — while subsoil, clay and rock usually need hauling away, which is charged by volume or weight. Disposal and trucking are often the biggest line items in an excavation, so the loose-volume figure is the one that drives the budget.
Backfill and what fills the hole
Most excavations are not left empty: footings receive concrete, trenches receive pipe and bedding, and slabs receive gravel base. Calculate the backfill or fill material separately — the related concrete, gravel and footing calculators handle the common cases. Knowing both the dig-out and the fill-in volumes up front keeps the project moving without surprise orders or surprise disposal bills.
Planning what happens to the spoil
Every excavation produces spoil, and deciding its fate early shapes the budget. Clean topsoil stripped from the surface is valuable — set it aside on a tarp for reuse in beds and grading rather than hauling it away and buying it back. Subsoil, clay and rock usually have to be removed, and disposal is charged by volume or weight, often the largest single cost of an excavation. The loose (swelled) volume is what drives trucking and tipping fees, since that is what actually fills the trucks. Knowing the swelled figure up front lets you book the right number of loads and avoid surprise disposal bills.
Safety in trenches and deep digs
Excavation is among the most dangerous construction activities because of cave-ins, which happen without warning and are frequently fatal. Soil is far heavier than it looks — a cubic yard can exceed a ton — and an unsupported trench wall can collapse in an instant. Never enter a deep, unsupported trench: walls must be sloped back to a safe angle, benched, or shored with a trench box, per safety regulations that scale with depth. Keep spoil piles back from the edge so their weight does not surcharge the wall and trigger collapse. For anything beyond a shallow dig, this is professional, regulated work.
Locating utilities first
Before any digging, locate buried utilities — gas, electric, water, sewer, telecom. In many regions a free call-before-you-dig service marks them out, and using it is often legally required. Striking a gas or electric line is potentially lethal and always expensive. Hand-dig carefully near marked lines rather than trusting a machine. This step costs nothing but a phone call and a few days' wait, and it is non-negotiable; the most accurate volume estimate in the world does not help if the dig hits a live service.
Backfill and compaction
Most excavations are refilled, and how you backfill matters as much as how you dug. Backfill in compacted lifts — adding soil in layers and compacting each — rather than dumping it all and hoping it settles, which leaves voids that subside later and crack whatever sits above. Around foundations and under slabs and pavements, granular fill that compacts reliably is used rather than the original spoil. Footings, slabs and pipe bedding each have their own fill requirements, sized by the related concrete, gravel and footing calculators. Plan the dig-out and the fill-in together so the project flows without idle equipment or repeat orders.
Estimating cost and hiring equipment
Excavation cost is driven less by the digging than by what happens to the spoil and how safely the dig is done. The calculator's in-ground and swelled volumes let you size disposal and trucking, often the largest line items, since disposal is charged by the loose volume that fills the trucks. Small jobs can be hand-dug; anything sizeable warrants a rented mini-excavator and operator, or a contractor, both for speed and because deep digs demand the sloping, benching or shoring that safety requires. Before any dig, the free call-before-you-dig utility locate is essential and often legally required — striking a buried service is dangerous and expensive. Budget for the machine or contractor, the disposal of unusable spoil by the load, and any shoring or trench protection. The swelled-volume figure is the one that drives the budget, so calculate it carefully, set aside reusable topsoil rather than paying to remove and replace it, and never compromise on trench safety to save time. A small over-dig for working room and sloped sides is normal and prudent, and it is far cheaper to estimate that generously up front than to discover mid-project that the hole needs widening, the spoil pile has nowhere to go, or an extra truck is needed to haul a volume the bare calculation understated.
Frequently asked questions
How do I calculate cubic yards of dirt?
Multiply length × width × depth in feet, then divide by 27. A 20×12 ft area dug 1 ft deep is 240 cu ft, or about 8.9 cubic yards in the ground.
What is soil swell and why does it matter?
Dug soil expands as it loosens — commonly by about 25%. So 9 cubic yards in the ground becomes around 11 loose cubic yards to haul away. Truck and disposal estimates should use the swelled (loose) volume.
How much does a cubic yard of dirt weigh?
About 1.1 to 1.3 tons for typical soil, more when wet. This matters for hauling, since trucks and disposal sites often charge or limit by weight.
How many dump truck loads is my excavation?
A standard dump truck holds roughly 10 to 14 cubic yards. Divide your loose (swelled) volume by the truck capacity to estimate loads — round up, since a partial load still counts.