Earthwork Excavation Calculator
Estimate excavation volume, total cost, and number of truck loads needed for any construction dig. Perfect for contractors, estimators, and project managers budgeting foundation, trench, or bulk earthworks.
About this calculator
Excavation volume is calculated using the simple prismatic volume formula: V = L × W × D, where L is the excavation length (m), W is the width (m), and D is the depth (m). The result is in cubic metres (m³). Total excavation cost is then: Cost = V × rate, where rate is the cost per cubic metre in dollars. The calculator also estimates truck loads by dividing the volume by a standard truck capacity (typically 10–12 m³ per load). In practice, a swell factor must be applied because loose excavated soil occupies more volume than in-situ material — typically 10–30% more depending on soil type (sand ≈ 10%, clay ≈ 20–30%). Contractors use this to avoid underestimating haulage and disposal costs, which can significantly affect project profitability.
How to use
You need to excavate a foundation 15 m long, 8 m wide, and 2.5 m deep in sandy soil at a cost of $25/m³. Step 1 — Volume: V = 15 × 8 × 2.5 = 300 m³. Step 2 — Cost: Cost = 300 × $25 = $7,500. Step 3 — Truck loads: assuming 10 m³ per truck and 15% swell factor, loose volume = 300 × 1.15 = 345 m³, so loads = 345 / 10 = 34.5 → 35 truck loads. Step 4 — Review these figures against your project budget and schedule to confirm plant and haulage requirements before mobilising.
Frequently asked questions
What is soil swell factor and why does it matter for excavation cost estimates?
Soil swell factor accounts for the increase in volume that occurs when soil is excavated from its natural, compacted state. A cubic metre of in-situ material becomes more than a cubic metre of loose, disturbed soil because air voids open up during digging. Sandy soils swell by roughly 10–15%, clays by 20–30%, and rock by 30–50%. If you ignore swell, you will underestimate the number of truck loads required to haul material away, leading to cost overruns and scheduling delays. Always multiply the in-situ volume by the appropriate swell factor when calculating haulage quantities.
How do I calculate the number of truck loads needed for an excavation project?
First calculate the in-situ excavation volume (L × W × D). Then apply the soil swell factor to get the loose (bulked) volume — for example, multiply by 1.20 for clay. Divide this bulked volume by the capacity of the dump trucks you are using; a standard 10-wheel truck typically carries 10–12 m³ per load. Round up to the nearest whole number since you cannot use a fraction of a truck trip. Also consider the truck cycle time, travel distance to the dump site, and any permit restrictions on truck gross weight that may reduce load capacity.
What factors affect the cost per cubic metre of excavation?
Excavation cost varies widely depending on soil type and hardness, equipment type (backhoe, bulldozer, or blasting for rock), site accessibility, excavation depth (deeper excavations require shoring and are slower), disposal distance, and local labour and fuel rates. Soft soils in accessible sites can cost as little as $10–20/m³, while hard rock removal requiring blasting or specialist equipment can exceed $100–200/m³. Seasonal conditions, mobilisation costs, and the volume of work also affect unit rates — larger projects typically command lower per-cubic-metre prices due to equipment utilisation efficiencies.