Excavation Calculator
37 yd³ loose, 4 loads.
| Volume | Amount | What it means |
|---|---|---|
| Bank | 29.63 yd³ | As it sits in the ground — the hole you are digging |
| Loose +25% | 37.04 yd³ | After digging — this is what gets hauled |
| Compacted −10% | 26.67 yd³ | If re-placed and compacted as engineered fill |
| Truck loads at 12 yd³, from the loose volume | 4 | Round trips to haul it away |
Bank and loose volume are not the same number, and the difference is what catches people out. Digging a cubic yard out of the ground does not give you a cubic yard in the truck — breaking the material up introduces voids, and it expands. Common earth swells about 25%, clay about 35%, and blasted rock 60%. Truck loads are counted from the loose volume, because that is what physically goes in the bed; using the bank volume would leave you a pile in the yard and short a trip. Shrinkage runs the other way: material re-placed and properly compacted ends up occupying less than it did in the ground, which is why backfilling a trench with its own spoil never quite fills it. Swell factors vary with moisture and how the material is dug — treat these as planning figures. This estimates a straight-sided excavation: sloped or benched sides for safety add volume, and any trench over 5 ft deep requires a protective system by OSHA rule. Call 811 before you dig.
Enter your dig dimensions to get bank and loose cubic yards using real soil swell factors, plus how many truck loads it takes to haul away.
Before you dig
Two things, both free, both non-negotiable:
- Call 811. Utilities mark their buried lines at no charge, usually within a few working days. In most jurisdictions it is legally required.
- Know the trench rule. Any excavation 5 feet deep or more needs a protective system — sloping, benching, shoring, or a trench box — unless it is cut in stable rock. A cubic yard of soil weighs well over a ton, and trench collapses are consistently fatal. This is not a corner to cut.
How to use this calculator
- Enter the dimensions of the excavation. Depth is in feet here, not inches.
- Pick the soil type. This sets the swell factor, which is the whole point of the calculation.
- Set your truck capacity — 10 to 14 yd³ for a tandem axle.
- Add a haul cost per load if you have a quote.
The formula
Bank = Length × Width × Depth · Loose = Bank × (1 + Swell%) · Compacted = Bank × (1 − Shrink%)
Truck loads = Loose volume ÷ Truck capacity, rounded up
Worked example — a 20 × 10 ft trench, 4 ft deep
Common earth at 25% swell, 12 yd³ truck.
- Bank volume: 20 × 10 × 4 = 800 ft³ = 29.6 yd³
- Loose volume: 29.6 × 1.25 = 37.0 yd³
- Compacted, if replaced: 29.6 × 0.90 = 26.7 yd³
- Truck loads: 37.0 ÷ 12 = 3.1 → 4 loads
Count from the bank volume instead and you get 29.6 ÷ 12 = 2.5, so 3 loads — and a substantial pile of soil left in the yard after the third truck leaves. That one distinction is what this calculator exists for.
Bank, loose, and compacted
The same material occupies three different volumes depending on what has happened to it, and every one of them is the right answer to a different question:
| State | What it is | Use it for |
|---|---|---|
| Bank | In place, as it sits in the ground | Sizing the hole; pricing excavation by the yard |
| Loose | After digging, broken up with voids between clumps | Hauling, truck loads, stockpile space |
| Compacted | Re-placed and mechanically compacted | Backfill volumes; how much imported fill you need |
In the ground, soil has been compressed by everything above it for a very long time. Digging destroys that structure and introduces air, which is why the pile is always bigger than the hole. Compaction squeezes the air back out — and does it slightly better than nature managed, which is why compacted fill ends up occupying less than bank volume.
Swell factors by soil type
| Material | Swell | 1 yd³ bank becomes |
|---|---|---|
| Sand or gravel | 12% | 1.12 yd³ loose |
| Loam / common earth | 25% | 1.25 yd³ loose |
| Clay | 35% | 1.35 yd³ loose |
| Mixed soil and rock | 43% | 1.43 yd³ loose |
| Solid rock, broken | 60% | 1.60 yd³ loose |
The pattern: the more cohesive and structured the material was in place, the more it expands when broken apart. Sand was never tightly bound and barely swells; solid rock blasted into fragments occupies more than half again its original space.
Why your backfill will not fill the trench
Dig a trench, lay a pipe, and shovel the spoil back in. At first it heaps above grade, because the loose material is 25% bigger than the hole it came from. Over the next few months it settles, and if you compact it properly it ends up below grade — because compacted fill occupies less than the original bank volume.
This is normal and expected. It is why utility trenches across lawns are left mounded, and why you should plan on topping up with imported fill a season later rather than assuming the spoil will balance out.
Weight, not volume, often limits the truck
A tandem-axle dump truck might be rated for 14 cubic yards, but legal axle weights frequently bind first. Dry sand runs around 2,700 lb per cubic yard; saturated clay can exceed 3,000. At those weights a truck hits its legal limit at 8 or 9 yards, well before the bed is full.
Ask your hauler what they can actually carry of your material rather than assuming the bed volume. The difference of a load or two matters when each trip carries a fixed charge.
What this calculator does not include
- Sloped or benched sides. Safe excavation of anything deep means cutting the sides back, which adds substantial volume — often far more than people expect.
- Over-excavation for working room around footings and foundations.
- Topsoil stripping and stockpiling separately from subsoil.
- Dewatering, rock breaking, or removal of unexpected obstructions.
- Tipping fees at the disposal site, which are usually separate from haulage.
Common mistakes to avoid
- Counting truck loads from bank volume. Use loose. This is the mistake this calculator is built around.
- Assuming the spoil will backfill the hole. It over-fills, then settles short.
- Estimating vertical sides on a deep dig. Sloping adds volume, and safety requires it.
- Ignoring weight limits. Wet material fills a truck by weight long before volume.
- Digging before calling 811. Free, fast, and legally required in most places.
How we calculate this
Bank volume is length × width × depth as measured in the ground. Loose volume applies the soil's swell percentage, and compacted volume applies its shrink percentage. Truck loads are counted from the loose volume, because that is what physically goes into the bed — counting from bank volume is the classic way to end up a trip short with a pile left in the yard. Swell factors are the standard planning figures: 12% for sand and gravel, 25% for common earth, 35% for clay, 43% for mixed soil and rock, and 60% for solid rock. Real swell varies with moisture and excavation method. This assumes straight, vertical sides.
Sources
Frequently asked questions
How do I calculate excavation volume?
Multiply length by width by depth for the bank volume — the material as it sits in the ground. Then multiply by the swell factor for your soil to get the loose volume, which is what actually goes in the truck. A 20 by 10 foot trench 4 feet deep is 800 cubic feet, or 29.6 cubic yards bank, which becomes 37 cubic yards loose in common earth.
What is the difference between bank, loose, and compacted volume?
Bank volume is the material in place in the ground. Loose volume is the same material after digging, which is larger because breaking it up introduces voids — this is the number that matters for hauling. Compacted volume is what it occupies after being re-placed and compacted, which is smaller than bank. All three describe the same material.
What is the swell factor for soil?
Sand and gravel swell about 12%, common earth or loam about 25%, clay about 35%, mixed soil and rock about 43%, and solid broken rock as much as 60%. The wetter and more cohesive the material, the more it swells. These are planning figures — actual swell varies with moisture and how the material is dug.
How many cubic yards does a dump truck hold?
A tandem-axle dump truck typically carries 10 to 14 cubic yards, and a single-axle around 5 to 7. But weight often limits the load before volume does: wet clay is far heavier per yard than dry sand, so a truck rated for 14 yards of light material may only take 8 or 9 yards of saturated soil. Ask your hauler what they can legally carry.
Why does soil take up more space after digging?
Because in the ground it has been compacted by everything above it for a very long time. Digging breaks that structure apart and introduces air voids between the clumps. A cubic yard of clay in place becomes about 1.35 cubic yards of loose clay in a pile, and it will not go back into the same hole without compaction equipment.
Why won't the spoil fill the trench back up?
It will over-fill it at first, then settle below grade. Freshly dug material is loose and occupies more space than it did in the ground, so the trench looks over-filled. Over the following months it settles — and compacted properly it ends up occupying less than the original bank volume, leaving a depression. That is normal, and it is why utility trenches are usually mounded and then topped up later.
How deep can I dig without shoring?
Under OSHA rules, any trench 5 feet deep or more requires a protective system — sloping, benching, shoring, or a trench box — unless it is cut entirely in stable rock. Trench collapse kills people every year, and a cubic yard of soil weighs well over a ton. If you are digging deep, this is not the place to save money.
Do I need to call before digging?
Yes, always, and in most places it is legally required. Call 811 in the United States and utilities will mark their buried lines free of charge, usually within a few working days. Hitting a gas line or a fibre trunk is dangerous and extremely expensive. It costs nothing and takes one phone call.