Excavation Calculator
Work out excavation volume in bank and loose cubic yards, allowing for soil swell, with truck loads, haul weight and cost.
How to use this calculator
- 1Pick the shape of the excavation and enter its dimensions, or enter a known bank volume directly.
- 2Choose the soil type. If you have a geotechnical report, use its swell figure with the Custom option.
- 3Enter anything you will backfill on site, then read the loose volume, truck loads and haul weight.
How the calculation works
loose = bank × (1 + swell) loads = max(⌈loose ÷ capacity⌉, ⌈weight ÷ limit⌉)- bank
- Volume of soil undisturbed in the ground — the size of the hole, in cubic yards
- loose
- Volume of the same soil once excavated, in the pile or the truck
- swell
- Fractional expansion on digging: 0.12 for sand, 0.25 for earth, 0.40 for clay, 0.65 for blasted rock
- capacity
- What one truck holds by volume, in loose cubic yards
- weight ÷ limit
- Haul weight against the legal load limit — the constraint that governs with dense or wet material
Bank volume is the hole. Loose volume is the pile. They are different numbers for the same soil, and hauling is priced on the pile.
Swell is a percentage of bank volume, so 100 bank yd³ of clay at 40% swell becomes 140 loose yd³. It is not reversible by subtracting the same percentage: going from loose back to bank divides by 1.40, giving 71%.
Truck loads are limited by whichever runs out first — the bed volume or the legal axle weight. Dense or wet material hits the weight limit with the bed half empty.
Worked example
A 30 × 20 × 8 ft basement in ordinary earth
- 1.Volume in the ground: 30 × 20 × 8 = 4,800 ft³, which is 4,800 ÷ 27 = 177.8 bank yd³.
- 2.Earth and loam swell 25%, so the spoil pile is 177.8 × 1.25 = 222.2 loose yd³.
- 3.At 12 yd³ per truck that is 222.2 ÷ 12 = 18.5, rounded up to 19 loads.
- 4.Weight check: 222.2 yd³ × 2,050 lb = 455,600 lb, or 227.8 tons. At a 15 ton limit that is 16 loads.
- 5.Volume governs here — 19 loads — so the trucks fill before they overload.
- 6.Estimating on the 177.8 yd³ hole instead would have called for 15 loads: four trucks short.
Result: 222.2 loose yd³, 19 loads
The same hole in clay, where weight governs
- 1.Clay swells 40%, so the same 177.8 bank yd³ becomes 248.9 loose yd³.
- 2.Backfilling 60 bank yd³ around the foundation leaves 117.8 bank yd³ of surplus.
- 3.That surplus swells to 117.8 × 1.40 = 164.9 loose yd³ to haul.
- 4.By volume: 164.9 ÷ 12 = 14 loads. By weight: 164.9 × 2,300 lb = 189.6 tons ÷ 15 = 13 loads.
- 5.Volume still governs, but only just — wetter clay would flip it.
Result: 164.9 loose yd³, 14 loads
The hole and the pile are not the same size
Soil in the ground has been compacted by its own weight over geological time. Digging it up breaks that structure and introduces voids, so the material that comes out occupies more space than the hole it left. The industry calls this swell, and it is measured as a percentage of the in-ground, or bank, volume.
The size of the effect is larger than most people expect. Sand and gravel gain about 12%. Ordinary earth and loam gain 25%. Clay gains 40%, because it comes out in clods that pack badly. Blasted rock gains 65%. Estimating haulage from the hole rather than the pile therefore under-orders trucks by a fifth to a half.
Note also that swell is not reversible by subtracting the same percentage. Clay at 40% swell means 100 bank yards become 140 loose yards; converting 140 loose back to bank divides by 1.40, which is a 29% reduction, not 40%.
Bank, loose and compacted — three volumes for one soil
Earthwork uses three measures and they are all different. Bank cubic yards describe soil in the ground. Loose cubic yards describe it in the truck or the stockpile. Compacted cubic yards describe it after it has been placed and rolled in a fill.
Compacted volume is usually *smaller* than bank volume, because engineered fill is compacted harder than nature managed. This is why importing fill almost always costs more than the cut volume suggests: to place 100 compacted yards you may need to buy 110 bank yards, which arrives as around 135 loose yards on trucks.
For excavation and haul-off, bank and loose are the two that matter — which is what this calculator reports. If you are placing fill, get the shrinkage figure from your geotechnical report rather than assuming.
When trucks run out of weight before they run out of room
A dump truck has two limits: the volume of its bed and the legal weight of its axles. Which one you hit first depends on the density of the material, and for excavation spoil it is often the weight.
Loose earth runs about 2,050 lb per cubic yard, clay 2,300, and wet rock or hardpan close to 2,800. A truck rated 15 tons reaches that limit at roughly 14 yards of loose earth but only 10 yards of rock — so it leaves with the bed visibly not full. Rain makes this dramatically worse, since saturated soil can gain several hundred pounds per yard.
This calculator checks both limits and reports whichever needs more loads, because the one that governs is the one you pay for.
Depth is a safety threshold, not just a number
US federal rules require protective systems in any excavation 5 feet deep or more that workers enter, unless it is cut entirely in stable rock. Below that depth a competent person still has to assess the ground.
Protection means sloping the walls back, benching them in steps, or installing a shield or shoring. Sloping in particular adds substantial volume: a 10 ft deep excavation laid back at the 1.5:1 slope required for the softest soil class adds 15 ft of width on every side, which can more than double the dig.
This calculator computes a vertical-sided volume. If your excavation needs sloping, model the sloped top dimensions instead, and treat that as an estimate rather than a plan.
What this assumes, and where it stops
Assumptions
- Excavation walls are vertical, with no allowance for sloping, benching or shoring.
- Ground is level, so the depth entered is the depth everywhere.
- Swell percentages are the standard earthwork values for the soil type chosen, at natural moisture content.
- Backfill is measured as bank volume — the in-ground volume it fills, not the loose volume delivered.
- Trucks fill to their stated capacity, and the weight check uses typical loose densities for each soil.
Limitations
- Does not model sloping or benching, which on deep excavations can add more volume than the original dig.
- Assumes uniform soil. Real sites layer topsoil over subsoil over rock, each with a different swell factor and each usually priced differently.
- Compaction and shrinkage for placed fill are not calculated. Compacted fill occupies less than bank volume, so imported fill quantities are larger than a straight volume match suggests.
- Does not account for groundwater, dewatering, contaminated soil handling, or disposal restrictions — any of which can dominate the cost.
- Not a substitute for a site-specific geotechnical report or a trench safety plan.
Common questions
What is a swell factor?
The percentage by which soil expands when it is dug out of the ground. Soil in place has been compacted over time; excavating introduces voids, so the spoil pile is larger than the hole. Sand swells about 12%, ordinary earth 25%, clay 40% and blasted rock 65%. Haulage is billed on the swollen volume.
How many truck loads is my excavation?
Take the bank volume, multiply by one plus the swell factor to get loose yards, then divide by truck capacity — but check the weight limit too. A tandem dump truck holds 10 to 14 cubic yards, and with dense or wet material it often reaches its legal weight before the bed is full.
What is the difference between bank and loose cubic yards?
Bank cubic yards measure soil undisturbed in the ground, which is what defines the size of your hole. Loose cubic yards measure the same soil after excavation, in a pile or a truck. Loose is always the larger number, and it is the one that determines haulage. A third measure, compacted cubic yards, applies to placed fill and is smaller than bank.
How deep can I dig without shoring?
US federal rules require a protective system — sloping, benching, shoring or a trench shield — for any excavation 5 feet deep or more that a worker enters, unless it is cut entirely in stable rock. Shallower excavations still need assessment by a competent person. Always locate buried utilities before digging at any depth.
Sources
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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