Excavation Calculator
Enter a trench or footing's length, width, and depth to calculate the cubic yards of soil to excavate, plus the expanded (loose) volume for hauling, since dug soil takes up more space than it did compacted in the ground.
How the Excavation formula works
Compacted volume, then adjusted for soil swell:
Cubic yards (in-ground) = (Length × Width × Depth) / 27 Loose volume for hauling = Cubic yards × (1 + Swell factor)
Soil typically swells 20-30% once excavated, since loosened soil has more air gaps than compacted, undisturbed soil.
Step-by-step calculation
- Multiply length, width, and depth (in feet) to get cubic feet.
- Divide by 27 to convert to cubic yards — the in-ground volume.
- Increase by a swell factor (commonly 25%) to estimate the loose volume once dug, which is what actually needs hauling away.
Worked example
A trench 40 ft long, 2 ft wide, and 3 ft deep: Volume = 40×2×3 = 240 ft³ = 8.89 yd³ in-ground. With 25% swell, loose volume for hauling ≈ 11.1 yd³.
Frequently asked questions
Why does dug soil take up more space than before?
Undisturbed soil is compacted with minimal air gaps. Once excavated, it loosens and includes more air pockets between particles, increasing its volume — this is why the same amount of dirt needs more truck capacity to haul away than its original in-ground volume suggests.
Does swell factor vary by soil type?
Yes — sandy or loose soils swell less than dense clay, which can swell more significantly. 25% is a reasonable general estimate, but check with your excavation contractor for soil-specific figures if precision matters.