Excavation Calculator
Bank (in-situ) excavation volume and the larger, swollen loose volume once soil is dug out, plus an estimated weight.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Bank volume = Length × Width × Depth
Loose (swollen) volume = Bank volume × (1 + swell %)
Weight = Bank volume × in-situ soil density (weight does not change with swell)
Run the calculation to see each step with your own numbers.
A 10 ft × 8 ft footing excavation, 2 ft deep, common earth, default 25% swell.
Bank volume = 10 × 8 × 2 = 160 ft³ = 5.93 yd³ exact
Loose volume = 5.93 × 1.25 = 7.41 yd³ (what to size the truck/dumpster for)
Weight ≈ 4.53 m³ × 1,600 kg/m³ = 7,250 kg ≈ 8.0 US tons
- A rectangular, uniform-depth cut. A sloped/benched excavation (required by OSHA for most trenches over 5 ft) needs extra volume for the side slopes — not modelled here.
- Swell percentages are typical ranges; actual bulking depends on moisture, compaction history and handling equipment.
- Weight uses the soil's in-situ (undisturbed) bulk density and does not change when the soil is loosened — only the volume grows.
- Groundwater, shoring, rock breaking and haul distance are not included.
- Why is the 'recommended' volume bigger, not smaller?
- Unlike most BuildFactor calculators, where 'recommended' means extra material to buy, here it means the soil physically expands once dug up — loose soil takes up more room than it did packed in the ground. Size your truck or dumpster to the recommended (loose) figure, not the bank figure.
- Does the weight change once the soil is loosened?
- No — swelling only increases volume (the soil gets fluffier/less dense), the total mass stays the same. That's why the weight output doesn't get a waste-adjusted figure.
- What about a sloped trench or bench?
- OSHA generally requires sloping or benching for trenches deeper than 5 ft in most soil. That adds volume beyond a straight-sided box — treat this as the minimum, and add extra for the slope if one is required.
Geometry
Standard geometry: Volume = L × W × D.
Soil swell (bulking) percentages
Typical ranges by soil type (topsoil/common earth ≈25%, sand & gravel ≈15%, dense clay ≈35%, blasted rock ≈50–60%): Caterpillar Performance Handbook earthwork tables; USACE construction-estimating references. Actual bulking varies with moisture and handling.
In-situ density
Typical in-situ bulk densities by soil type: Engineering ToolBox 'Densities of common materials'; USDA soil bulk-density reference ranges.
About the Excavation Calculator
The Excavation Calculator gives the bank (in-situ, undisturbed) volume you're digging out of a footing, trench, pool or pad, and — because dug soil loosens and takes up more room than it did in the ground — the larger swollen volume you'll actually need to haul or stockpile. Weight is estimated from the selected soil's in-situ density, which does not change with swell (the mass is the same; only the volume grows). For fill you're bringing in rather than removing, use the Topsoil, Gravel or Cubic Yard calculators instead.
What you enter
- Length
- Width
- Depth — Measured from existing grade to the bottom of the cut.
- Soil type — Sets the default swell allowance and density below — both editable.
- Waste allowance — Default 25%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Excavation volume (bank, in-situ) — Recommended = swell-adjusted loose/hauled volume, not extra material to buy.
- Estimated in-situ weight — Mass doesn't change when soil swells — only its volume does.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Topsoil Calculator — Topsoil by volume and by delivered weight for a lawn, bed or fill area from its area and depth.
- Gravel Calculator — Gravel by volume and by delivered weight for driveways, paths and fill.
- Cubic Yard Calculator — Convert a length, width and depth into cubic yards, cubic feet or cubic metres.
- Plastering Calculator — Plaster (render) volume, plus cement bags and sand, for a wall or ceiling area from its thickness and mix ratio.
- Bituminous Prime & Tack Coat Calculator — Bituminous prime coat or tack coat material for a paved area from its application rate.
- Air Conditioner (BTU) Sizing Calculator — Estimated BTU/hr cooling capacity for a room, and the nearest standard-size unit, from the room area and a few adjustment factors.
Part of the Landscaping & Driveway calculators.