Calculate backfill volume in cubic yards and tons for pits, trenches, and annular excavations. Enter your excavation and structure dimensions to get net backfill, including swell factor and compacted volume.
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Shop Express Tools →Backfill volume = Excavation volume − Structure volume. For a trench: (Length × Width × Depth) ÷ 27 = CY excavation. Subtract the pipe or structure CY. Multiply by swell factor (1.10–1.30) for the loose material volume you need to import. Add 10% for compaction loss.
Earthwork volume calculations must account for the difference between in-place (bank) measure and loose (hauled) measure. When soil is excavated, it loosens and expands in volume. This expansion is called swell. Conversely, when you compact fill material, it shrinks back. Understanding these factors prevents costly over- or under-ordering:
| Material | Swell Factor | Compaction Factor | Notes |
|---|---|---|---|
| Clean sand / gravel | 1.10–1.15 | 0.90–0.95 | Best for pipe zone backfill |
| Mixed sandy soil | 1.15–1.20 | 0.88–0.92 | Common native fill |
| Clay / silty clay | 1.20–1.30 | 0.85–0.90 | High swell; avoid near pipes |
| Dense clay | 1.25–1.35 | 0.82–0.88 | Hard to compact; prone to shrinkage cracks |
| Rock (blasted) | 1.30–1.50 | 1.00–1.10 | No compaction; large voids |
| Topsoil / organic | 1.10–1.20 | 0.75–0.85 | Avoid for structural backfill |
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Start free trialBackfill volume = excavation volume minus the volume occupied by the structure or pipe. For a rectangular pit, that's (length × width × depth) ÷ 27 for cubic yards, minus any structure. Add a swell factor (typically 10–20%) for material ordering.
When soil is excavated, it loosens and expands — this is called swell. Clay can swell 20–30%, sandy soil 10–15%, and rock 30–40%. This means you may need more material volume than the in-place (bank) volume suggests.
Typical compacted fill weighs approximately 1.2–1.5 tons per cubic yard depending on material type. Sandy fill is around 1.35 tons/CY, clay is heavier at 1.4–1.5 tons/CY. This calculator uses 1.35 as a general estimate.
Compaction factor is the ratio of compacted volume to loose volume. Well-graded granular fill typically compacts to about 85% of its loose volume (compaction factor 0.85). Specify compaction requirements (e.g., 95% proctor) in your plans.
Clean granular material (sand or gravel) is ideal for trench backfill around pipes for drainage and easy compaction. Native soil can be used in upper lifts. Avoid clay, organic material, or frozen soil for pipe zone backfill.
Enter excavation dimensions, then optionally enter the structure/footing size to subtract from backfill.