Excavation Calculator
This excavation calculator gives the volume of a dig in bank and loose yards, how many truck loads that is once the soil swells, and what the haulage costs.
Dig Volume
Truck Loads
What leaves the site. Trucks are paid by the loose yard, and soil swells the moment it is dug.
Excavation Cost
How to use the Excavation Calculator
Enter the dig and pick the soil. You get two volumes, and they are not the same number: bank yards are what the hole measures, and loose yards are what comes out of it once the soil breaks up.
That difference is swell, and it is why the Hauling tab exists. Trucks charge by the loose yard, so a 89 bank yard hole is 111 loose yards of clay and ten tri-axle loads, not eight.
Excavation formula
bank volume = length × width × depthloose volume = bank × (1 + swell%)compacted volume = bank × (1 − shrink%)loads = ceiling(loose volume ÷ truck capacity)
Every soil has its own swell, and rock is the extreme case, broken rock takes about two thirds again as much room as it did in the ground, and it never goes back.
| Soil | Swell | 1 bank yd³ becomes | Compacted, against bank |
|---|---|---|---|
| Topsoil / loam | 25% | 1.25 loose yd³ | −10% |
| Sand and gravel | 12% | 1.12 loose yd³ | −12% |
| Clay | 25% | 1.25 loose yd³ | −10% |
| Broken rock | 65% | 1.65 loose yd³ | +15% |
Rock is the exception in both columns. Soil placed and rolled ends up occupying less than the hole it came from. Broken rock does not, once it is blasted or ripped it cannot be re-consolidated, so a compacted rock embankment takes up more room than the excavation that produced it. That is why rock cut usually generates surplus fill rather than consuming it.
Rock swell varies with the rock: about 61% for sandstone, 63% for limestone, 72% for granite and riprap and 79% for shale. The 65% used here is a middle figure, if you know the lithology, use its own number.
Worked example
A 30 × 20 ft basement dig, 4 ft deep, in clay, with 10% over-dig:
- Volume: 30 × 20 × 4 = 2,400 ft³ = 88.9 bank yd³
- Plus 10% over-dig: 97.8 bank yd³
- Swelled at 25%: 122.2 loose yd³
- Tri-axle loads at 12 yd³: 11 loads
Estimating the haulage on the bank figure would have booked 9 loads. The two extra are the swell, and they are not optional.
What the result means
Bank, loose and compacted are three different volumes of the same soil. Bank is in the ground, loose is on the truck, compacted is back in place and rolled. Contracts and quotes are not always clear which one they mean, and that ambiguity is worth resolving before the work starts.
Excavation is usually priced by the bank yard and haulage by the load. That is why the cost tab keeps them apart, the digging is measured off the drawing, the trucking is measured off the swelled volume.
Backfill takes more material than the hole holds. Compacted fill occupies less space than the same soil did undisturbed, so importing fill for a 100 bank yard void needs about 110 bank yards from the borrow pit.
Common mistakes
- Booking trucks on bank measure. Under-orders haulage by 12 to 50 percent depending on the soil.
- Assuming one swell factor. Sand swells 12 percent, rock 65. On a big dig that is the difference between a handful of loads and a great many.
- No over-dig allowance. Sides are never vertical and floors are never flat. Ten percent is a starting point, more in loose ground where the sides need battering back.
- Forgetting the topsoil strip. It usually comes off first, is stockpiled separately and goes back at the end, a separate volume from the main dig.
- Not calling for utility locates. Free, legally required in most places, and the one omission that turns a dig into an incident.
Frequently asked questions
How do I calculate excavation volume?
Multiply length by width by depth and divide by 27 to get cubic yards. A 30 by 20 foot hole 4 feet deep is 2,400 cubic feet, which is 88.9 bank cubic yards, the volume as it sits in the ground.
What is soil swell?
The increase in volume when soil is dug and broken up. Clay and topsoil swell about 25 percent, sand and gravel about 12, and broken rock about 65. One cubic yard in the ground becomes 1.25 loose yards of clay on the truck, or 1.65 loose yards of rock.
How many truck loads is my excavation?
Take the bank volume, apply the swell factor for the soil, then divide by the truck capacity. A 98 bank yard dig in clay swells to 122 loose yards, which is 11 loads on a 12 yard tri-axle. Working from bank measure would have booked 9.
What is the difference between bank and loose cubic yards?
Bank yards are measured in the ground before digging. Loose yards are measured after, when the soil has broken up and taken on air. Excavation is usually priced per bank yard and hauling per loose yard, so it matters which one a quote refers to.
How much fill do I need to backfill a hole?
More than the hole measures. Compacted fill shrinks about 10 percent relative to bank measure, so filling a 100 cubic yard void to a compacted state needs roughly 110 bank cubic yards from wherever you are importing it.
How much does excavation cost per cubic yard?
Digging is commonly quoted per bank cubic yard and hauling per truck load, and the two are separate lines. Rates swing widely with access, soil, depth, water and how far the spoil has to travel, so treat any figure here as a placeholder for a real quote.
Sources and assumptions
Swell and shrink factors follow Caterpillar’s published loose and bank densities and state DOT shrinkage factors. Caterpillar puts common earth at 24 to 26 percent swell and sand at about 12.5, which is where those figures come from. Rock swell follows the FHWA Federal Lands earthwork tables, 61 percent sandstone, 63 limestone, 72 granite and riprap, 79 shale, and Caterpillar’s crushed-stone load factor, which implies 67. The 65 percent used here is a middle value.
The compacted figure for rock is positive against bank because broken rock cannot be re-consolidated. Soils shrink when placed and rolled; rock does not.
All of these vary with moisture, compaction and how the material is handled. They are approximations, a soils report governs on a designed job.
Truck capacities are nominal. Legal payload is limited by weight, not volume, so a heavy wet clay may fill a truck to its axle limit before the box is full.
Over-dig allowance covers ragged sides and an uneven floor. It does not cover battering slopes back for stability, benching or shoring, which are safety requirements sized by soil type and depth.
Call for utility locates before digging. It is free and legally required in most jurisdictions. Trench safety at depth is governed by OSHA and local regulation and is outside this calculation.
Trench safety is regulated, not advisory. OSHA publishes the requirements for sloping, benching and shoring at Trenching and Excavation, and anything deeper than five feet needs a protective system.