Bulk Density and Swell Factors of Common Earthwork Materials
A surveyed volume becomes tonnes, truckloads and payment only through a density — and the right density depends on whether the material is in the ground, loose in a pile or compacted in a fill. This reference gives loose and bank densities, load factors and the swell they imply for 20 common materials, and shows how to use them without mixing the states.
Bank, loose and compacted
Bank volume is material as it lies in place — what a survey of an excavation measures. Loose volume is the same material after digging, swollen by the voids between its pieces — what a stockpile survey measures. Compacted volume is material placed and rolled in a fill.
The load factor links them: loose volume = bank volume ÷ load factor, and swell = 1 ÷ load factor − 1. Tonnage is always volume × the density of the same state: bank volume with bank density, loose volume with loose density.
Reference table
Values from the Caterpillar material density tables; swell is derived from the load factor. The source notes that weight varies with moisture, grain size and compaction, and that tests are needed to fix exact values — treat the table as a starting point, not a measurement.
| Material | Loose (kg/m³) | Bank (kg/m³) | Load factor | Swell |
|---|---|---|---|---|
| Clay, natural bed | 1,660 | 2,020 | 0.82 | 22% |
| Clay, dry | 1,480 | 1,840 | 0.81 | 23% |
| Clay, wet | 1,660 | 2,080 | 0.80 | 25% |
| Clay and gravel, dry | 1,420 | 1,660 | 0.85 | 18% |
| Clay and gravel, wet | 1,540 | 1,840 | 0.85 | 18% |
| Earth, dry packed | 1,510 | 1,900 | 0.80 | 25% |
| Earth, wet excavated | 1,600 | 2,020 | 0.79 | 27% |
| Earth, loam | 1,250 | 1,540 | 0.81 | 23% |
| Gravel, pit-run | 1,930 | 2,170 | 0.89 | 12% |
| Gravel, dry | 1,510 | 1,690 | 0.89 | 12% |
| Gravel, dry, 6–50 mm | 1,690 | 1,900 | 0.89 | 12% |
| Gravel, wet, 6–50 mm | 2,020 | 2,260 | 0.89 | 12% |
| Sand, dry loose | 1,420 | 1,600 | 0.89 | 12% |
| Sand, damp | 1,690 | 1,900 | 0.89 | 12% |
| Sand, wet | 1,840 | 2,080 | 0.89 | 12% |
| Sand and clay, loose | 1,600 | 2,020 | 0.79 | 27% |
| Sand and gravel, dry | 1,720 | 1,930 | 0.89 | 12% |
| Sand and gravel, wet | 2,020 | 2,230 | 0.91 | 10% |
| Crushed stone | 1,600 | 2,670 | 0.60 | 67% |
| Topsoil | 950 | 1,370 | 0.70 | 43% |
Worked examples
A stockpile survey measures loose material. A 904.8 m³ pile of dry sand and gravel at 1,720 kg/m³ loose is 904.8 × 1.72 = 1,556 t.
An excavation survey measures bank material. 1,000 m³ of clay in its natural bed (load factor 0.82) becomes 1,000 ÷ 0.82 = 1,219.5 m³ loose, which is 82 loads for a 15 m³ body. Its weight is 1,000 × 2.02 = 2,020 t in bank state, or 1,219.5 × 1.66 = 2,024 t loose — the same material, agreeing within the rounding of the load factor.
| Case | Calculation | Result |
|---|---|---|
| Stockpile of dry sand and gravel (loose) | 904.8 m³ × 1.72 t/m³ | 1,556 t |
| Excavation in natural-bed clay (bank) → loose | 1,000 m³ ÷ 0.82 | 1,219.5 m³ |
| Truckloads, 15 m³ body | 1,219.5 ÷ 15 = 81.3 | 82 loads |
| Tonnage of that excavation | 1,000 m³ × 2.02 t/m³ | 2,020 t |
Measure your own material
Table values hide a wide spread: moisture, grading and how the material was dug all move them. For tonnage that someone will pay or be paid for, weigh a few loaded trucks against their surveyed loose volume, and measure bank density in place. Compacted fill has its own shrinkage, which this table does not give — measure it on site.
In STREAM the density is entered per stockpile, so each material in a yard can carry its own measured value; the report shows the resulting volume and tonnage.
Frequently asked questions
What is the difference between bank, loose and compacted volume?
Bank volume is material in place, loose volume is the same material after excavation (larger, because of the voids between pieces) and compacted volume is material placed and rolled in a fill. Loose volume = bank volume ÷ load factor.
How do you calculate the swell factor from the load factor?
Swell = 1 ÷ load factor − 1. A load factor of 0.82 means 1 ÷ 0.82 − 1 ≈ 22% swell; crushed stone at 0.60 swells about 67%.
Which density should I use for stockpile tonnage?
The loose density, because a stockpile survey measures loose material. Use bank density only with bank volumes, such as an excavation measured in place.
How accurate are table densities?
They are starting values. The source itself notes that weight varies with moisture, grain size and compaction and that tests are needed; weigh loaded trucks or measure density in place for any quantity that is paid for.
Sources
Measure stockpile volume and tonnage in STREAM
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