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Volumes are calculated in cubic yards at 27 cubic feet each.
- Excavated soil swells when loose and shrinks when compacted, so bank, loose and compacted volumes all differ for the same material.
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The arithmetic is easy. The states of the material are where the questions are.
Three volumes for one pile of dirt
| State | Means |
|---|---|
| Bank | In place, undisturbed, as measured in the ground |
| Loose | Excavated and in a truck, which is more volume |
| Compacted | Placed and compacted, which is less volume than bank |
Excavate a cubic yard and you haul more than a cubic yard. Place and compact it and it occupies less than a cubic yard.
A hole needing 100 cubic yards of compacted fill needs more than 100 cubic yards of bank material to supply it. Ordering to the compacted figure leaves the job short, and questions are built exactly there.
The conversion
Twenty-seven cubic feet to a cubic yard. Every earthwork and concrete calculation runs through it.
Calculate excavation volume from dimensions
For a rectangular excavation, multiply length by width by depth to get cubic feet, then divide by 27 to convert to cubic yards. Convert every dimension to the same unit first. A trench 60 feet long, 3 feet wide, and 4 feet deep contains 720 cubic feet, or 26.67 bank cubic yards before any allowance for swell, shrink, waste, or unsuitable material.
For changing cross sections, the average-end-area method estimates volume between two stations: multiply the station spacing by the average of the two end areas. If the end areas are measured in square feet and distance is in feet, divide the resulting cubic feet by 27 for cubic yards. The method estimates the interval; more closely spaced sections usually represent irregular ground more accurately.
| Quantity | Meaning | Use in estimating |
|---|---|---|
| Bank volume | Soil in its natural, undisturbed state. | Usually the excavation quantity before it is loosened. |
| Loose volume | Excavated soil after it expands during digging and handling. | Useful for truck capacity and haul planning. |
| Compacted volume | Placed soil after it is spread and compacted. | Use for required fill; conversion from bank or loose volume depends on the material and specification. |
Swell and shrink factors are soil-specific assumptions supplied by geotechnical information, plans, or the estimating basis. Do not treat a memorized factor as universal. If an example states that a soil swells 25%, then 100 bank cubic yards become 125 loose cubic yards for hauling. A separate compaction or shrink factor is needed to determine compacted fill yield.
Length times width times depth in feet, divided by 27. Depths in inches convert to feet first, and forgetting that is the other common error. Lifts too thick is the failure.
Compaction
Specified as a percentage of a laboratory maximum density, tested in the field. Achieving it depends on moisture content, lift thickness and the right equipment for the soil. Twenty-seven. Learn it.
Placing lifts too thick is the usual failure. The top compacts and the bottom does not, and it passes a surface test while settling later. It settles later.
Cut and fill
Balancing them on site avoids hauling material in or out, which is often the largest single cost in earthwork.
Common questions
How many cubic feet in a cubic yard?
27, and every earthwork and concrete calculation runs through it.
What are bank, loose and compacted volumes?
The same material in place, excavated, and placed and compacted. All three differ.
Why do fill quantities catch people?
A hole needing 100 cubic yards compacted needs more than 100 cubic yards of bank material to supply it.
How is compaction specified?
As a percentage of a laboratory maximum density, tested in the field.
What is the usual compaction failure?
Lifts placed too thick, so the top compacts and the bottom does not, settling later.