Excavation Volume Calculator
Calculate in-situ excavation volume and an estimated loose spoil volume using an editable bulking factor.
Use calculator →Groundworks Calculators — Excavation, Aggregate & Skip Planning
Free UK groundworks calculators for excavation, trenches, MOT Type 1, aggregates and skip planning. Estimate volumes, tonnes, bags and spoil with transparent assumptions.
Trench Volume Calculator
Calculate trench excavation volume from length, average width and average depth.
Use calculator →MOT Type 1 Calculator
Estimate sub-base cubic metres and tonnes from area, compacted depth and an editable supplier density.
Use calculator →Aggregate Bag Calculator
Convert an aggregate requirement in tonnes into small bags or bulk bags using the actual bag weight.
Use calculator →Skip Size Calculator
Estimate a nominal UK skip size from loose waste volume, cubic-yard conversion and an editable usable-fill allowance.
Use calculator →Aggregate Tonnage Calculator
Calculate aggregate tonnes from area, finished depth, ordering allowance and an editable bulk density.
Use calculator →Which Groundworks calculator should you use?
Excavation & trenches
Use the Excavation Volume Calculator for general dig volume and loose spoil, or the Trench Volume Calculator for linear excavations such as footings, drainage runs and service trenches.
Sub-base & aggregate
Use the MOT Type 1 Calculator for compacted sub-base planning, the Aggregate Calculator for tonnes from area and depth, or the Aggregate Bag Calculator when buying by bag weight.
Waste & skips
Use the Skip Size Calculator after you have estimated loose waste volume. Skip volume is only one constraint; dense waste can hit supplier weight limits first.
A simple Groundworks estimating workflow
For most jobs, keep the quantities in this order: measure the geometry → calculate the base volume → separate loose or compacted volume where relevant → convert using product/supplier data → round to the real sales or disposal unit. That prevents several common errors, especially treating excavated spoil, compacted sub-base and delivered aggregate as though they were the same volume.
Groundworks quantity questions these tools answer
- How many cubic metres will I excavate?
- How much loose spoil could a trench or excavation produce?
- How many tonnes of MOT Type 1 or aggregate might I need?
- How many bulk bags or small bags does that tonnage represent?
- What nominal skip size should I discuss with the supplier?
For full-job planning rather than a single quantity, use the Excavation & Skip Planning Guide, Driveway Materials Estimator and other project planners.
Groundworks estimating rule
Use these calculators to produce a transparent planning quantity, then verify the job against current drawings, actual site dimensions, product specifications and supplier data. Quantity tools cannot establish structural adequacy, excavation safety, drainage design, waste classification or legal payload.
How to use the Groundworks calculators accurately
Groundworks quantities become easier to audit when in-situ excavation, loose spoil, compacted layers, delivered volume and delivered mass are kept as separate values. Do not hide material-specific assumptions inside the arithmetic.
Four checks that improve the estimate
- Measure the real area, length, width and average depth before applying any bulking or ordering allowance.
- Use a bulking factor only after calculating the measured in-situ excavation volume.
- Use current supplier/product density when converting aggregate cubic metres into tonnes.
- Treat skip size as a planning value and confirm waste type, weight and loading restrictions with the supplier.
For product-dependent values such as density, bag weight, compacted depth or pack size, replace the calculator default with the current figure for the exact material you intend to buy.
Groundworks guides and reference data
Use the Groundworks guides when you need the method behind the number. Useful supporting pages include the Excavation & Spoil Guide, Aggregate Ordering Guide and Aggregate Bulk Density Guide.
Frequently asked Groundworks calculator questions
How do I calculate excavation volume?
For a simple rectangular excavation, multiply length by width by average depth in metres to get cubic metres. Keep any loose-spoil bulking factor as a separate second step.
How do I convert aggregate cubic metres to tonnes?
Multiply the adjusted aggregate volume by the relevant bulk density in tonnes per cubic metre. Use supplier or product data where available because density is not universal.
Is loose spoil volume the same as excavation volume?
No. Excavated material can occupy more volume after it is loosened, so the in-situ excavation and loose spoil should be shown separately.
Can I choose a skip using volume alone?
No. Nominal skip volume is only one constraint. Waste type, supplier rules and the weight of dense materials can limit the real load.