Excavation Volume Calculator
Determines the cubic volume of soil to remove for a rectangular excavation. Use it when planning foundations, pools, basements, or trenches to order skip bins or estimate disposal costs.
About this calculator
For a rectangular excavation pit, volume is calculated by multiplying its three dimensions: Volume = length × width × depth. All three measurements must be in the same unit (metres) so the result comes out in cubic metres (m³). One cubic metre of soil weighs roughly 1.5–1.8 tonnes depending on soil type, so this figure feeds directly into haulage and disposal cost estimates. Knowing the excavation volume also helps contractors order the right number of skip bins — a standard skip holds about 6–8 m³. For irregular shapes, break the area into rectangular sections, calculate each volume separately, and sum the results.
How to use
Suppose you are digging a rectangular trench for a house foundation: length = 12 m, width = 4 m, depth = 1.5 m. Apply the formula: Volume = length × width × depth = 12 × 4 × 1.5 = 72 m³. At a typical soil weight of 1.6 t/m³, you would need to dispose of roughly 115 tonnes of material. You would also need approximately 72 ÷ 7 ≈ 11 standard skip-bin loads. Enter your own dimensions to get an instant result.
Frequently asked questions
How do I convert excavation volume in cubic metres to tonnes of soil?
Multiply the cubic metre volume by the bulk density of your soil type. Typical loose topsoil has a density of about 1.2–1.4 t/m³, while compacted clay can reach 1.8 t/m³. For example, 72 m³ of average soil at 1.6 t/m³ equals 115.2 tonnes. Always confirm the soil density with a geotechnical report if precision matters for large projects.
What happens to excavation volume when soil is removed — does it expand?
Yes — this is called 'swell' or 'bulking'. When soil is excavated, it loosens and increases in volume by 20–40% depending on soil type. Clay soils swell more than sandy soils. So 72 m³ of in-situ soil might become 86–100 m³ of loose material in a truck. Factor this into skip-bin and haulage calculations to avoid underestimating transport costs.
Can I use this calculator for non-rectangular excavations like pools or trenches?
The calculator assumes a simple rectangular prism. For L-shaped or stepped excavations, divide the area into rectangular sections, calculate the volume of each section, and add them together. For tapered trenches with sloped walls, use the average width instead of the top width. Circular excavations (like for round pools) use a different formula: Volume = π × radius² × depth.