Excavation & Backfill Calculator — Dirt Volume & Hauling Estimator
Calculate trench, hole, or foundation excavation volume in cubic yards. Adjusts for bank soil density, spoil swell expansion, and backfill compaction requirements.
Soil in its natural undisturbed state is measured in Bank Cubic Yards (BCY). Once excavated, dirt expands to a larger volume measured in Loose Cubic Yards (LCY) due to added air (spoil swell). A standard dump truck holds exactly 10 cubic yards.
Understanding Soil Swell and Dirt Removal Logistics
A reliable dirt removal calculator must account for soil swell. Experienced site superintendents know that dirt occupies entirely different physical space depending on its compaction state:
- What is LCY meaning in construction? LCY stands for Loose Cubic Yards. When earth is excavated from its compacted, natural state (Bank Cubic Yards or BCY), it expands as air is introduced. This expansion is called "swell." You must calculate the LCY to know exactly how much volume of dirt you are hauling away.
- Hauling Based on LCY: Dump trucks are sized by LCY, not BCY. If you bid a hauling job using the BCY from your blueprint without using a spoil calculator or adjusting for the 15-30% swell factor, you will underestimate the number of dump trucks required and lose money on the excavation.
Bank Volume (BCY) = (Length × Width × Depth) ÷ 27
Loose Volume (LCY) = Bank Volume × (1 + (Swell% ÷ 100))
Compacted Volume (CCY) = Bank Volume × (1 - (Compaction% ÷ 100))
Dump Truck Loads = Ceil( Loose Volume (LCY) ÷ Truck Capacity )
Standard Soil Density & Swell Chart
| Soil Classification | Swell Factor % | Compaction Shrink % | Common Application |
|---|---|---|---|
| Clean Sand / Gravel | 10% - 15% | 10% - 15% | Backfilling slabs, foundation drainage. |
| Common Earth / Topsoil | 15% - 20% | 15% - 20% | Standard residential lawn & general site prep. |
| Heavy Clay | 20% - 25% | 20% - 25% | Ponds, structural sub-bases. High expansion danger. |
| Hard Rock / Blast Spoil | 30% - 40% | 0% (Varies) | Rock fill layers, retaining walls. Very high swell. |
Understanding Soil Swell and Excavation Volume
Excavation is rarely as simple as multiplying the length, width, and depth of a hole. When undisturbed earth (Bank Volume) is excavated, it introduces air voids and expands. This expansion is known as "soil swell," and calculating it accurately is critical for determining how many dump trucks are required to haul the spoil away.
Bank Volume vs. Loose Volume
There are two primary measurements in earthwork:
- Bank Cubic Yards (BCY): The volume of the soil in its natural, undisturbed state before excavation. This is the volume of the actual hole in the ground.
- Loose Cubic Yards (LCY): The volume of the soil after it has been excavated and loaded into a truck. This number is always larger than the BCY due to swell.
Common Soil Swell Factors
Different materials expand at vastly different rates when disturbed. Sand and gravel have low swell factors (typically 10% to 15%) because their granular nature limits air voids. Topsoil and common earth typically swell by 20% to 25%. Hard clays and blasted rock, however, can swell by up to 40% to 50% because the irregular chunks create massive voids when piled.
Hauling Logistics and Truck Sizing
A standard tandem-axle dump truck generally holds between 10 and 14 Loose Cubic Yards (LCY). When estimating excavation costs, failing to account for a 30% clay swell factor means you will underestimate the required number of trucks by nearly a third, destroying the profit margin on the dirt removal phase of the project.