Excavation Calculator
Calculate excavation volume in bank measure and the swelled volume that has to be hauled away.
Formula
Bank volume = Length × Width × Depth. Loose volume = bank volume × (1 + swell).
- Bank volume (m³) = L × W × D
- Loose volume (m³) = Bank volume × (1 + swell % ÷ 100)
- Truck loads = ceiling( Loose volume ÷ Truck capacity )
Worked example
A basement dig 10 m × 6 m × 1.5 m deep in clay with 25% swell, hauled in 12 m³ trucks.
- Bank volume = 10 × 6 × 1.5 = 90 m³
- Loose volume = 90 × 1.25 = 112.5 m³
- Loads = 112.5 ÷ 12 = 9.4, so 10 loads
90 m³ in the ground becomes 112.5 m³ of spoil — ten truck loads.
Assumptions and limitations
- The excavation is a rectangular prism with vertical sides. Battered or benched sides increase the volume significantly and must be calculated on the actual profile.
- Swell factor depends entirely on the material and its moisture. The default is a planning figure for common soils, not a value for your site.
- Truck loads assume trucks are filled to the stated heaped capacity. Weight limits often fill up before volume does, especially with wet or dense material.
- No allowance is made for working space around structures, which is usually required and adds real volume.
What this calculator does not do
- Does not assess trench or excavation stability. Battering, benching and support are temporary works matters that depend on ground conditions and depth.
- Does not classify the material or judge whether it can be reused. Suitability for backfill is a specification and testing question.
- Does not cover dewatering, rock breaking, existing services, or disposal charges at the tip.
Practical tips
- Weight, not volume, is usually what limits a haul truck on wet clay. Check the payload before assuming a 12 m³ body carries 12 m³.
- Add working space around any structure being built in the hole. Formwork and waterproofing need room, and that room is excavation you have to pay for.
- If some material is being reused as backfill, calculate the backfill first — you only haul away the difference.
Frequently asked questions
What is a swell factor?
Soil takes up more room once dug than it did in the ground because the particles are no longer packed. The swell factor is that increase — roughly 10–15% for sand, 20–35% for clay, and much more for blasted rock.
Do I pay for bank volume or loose volume?
It depends on the contract. Excavation is often measured in bank (in-situ) volume, while disposal is charged on loose volume or weight. Check which measure each rate refers to before you price it.
How many truck loads is my excavation?
Divide the loose volume by the truck capacity and round up. Remember that heavy wet material may hit the weight limit before the body is full.
Does this account for sloped or battered sides?
No. It calculates a rectangular prism with vertical sides. Battered excavations hold noticeably more volume, and the side slope required comes from your temporary works design and ground conditions.
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- Concrete Footing Calculator Calculate concrete for strip footings or a set of identical pad footings.
Estimating tool, not a design. This calculator works out quantities from the dimensions you enter. It does not size any structural member, verify a design, or confirm compliance with any building code. Check every result against your project specification and applicable local standards, and involve a qualified engineer where the work requires one.