How to use the excavation calculator
- Choose a rectangle or trench, or a round hole, and enter the size and depth.
- Enter how many identical holes (for example, 10 pier holes).
- Pick your soil type so the calculator can add swell.
- Enter your truck or skip size to see the number of loads, and a price per load for the hauling cost.
Excavation formulas
Bank volume = Length × Width × Depth (or π × r² × Depth) Loose volume = Bank volume × (1 + Swell %) Cubic yards = Cubic feet ÷ 27 Truck loads = Loose volume ÷ Truck capacity → round up
Worked example
Digging out a 20 × 10 ft area 3 ft deep in ordinary soil, hauled with a 10 yd³ truck:
- Bank volume = 20 × 10 × 3 = 600 ft³ = 22.2 yd³
- Loose volume = 22.2 × 1.25 = 27.8 yd³
- Truck loads = 27.8 ÷ 10 = 2.8 → 3 loads
Typical swell factors
| Material | Typical swell | 1 yd³ in the ground becomes |
|---|---|---|
| Sand / gravel | 10–15% | 1.10–1.15 yd³ |
| Common earth | 20–30% | 1.20–1.30 yd³ |
| Topsoil / loam | 25–35% | 1.25–1.35 yd³ |
| Clay | 30–40% | 1.30–1.40 yd³ |
| Broken rock | 50–70% | 1.50–1.70 yd³ |
The calculator uses the middle of each range. If your contractor quotes a different figure, choose “Custom” and enter it.
Common excavation jobs
- House or garage foundation: measure the outside of the footing plus working space on every side, and the depth from existing ground to the bottom of the footing.
- Pool: for an in-ground pool, add about 1 ft (300 mm) around the shell for the walls and backfill, and use the average depth plus the base thickness.
- Pier and post holes: use the round option with the number of holes.
- Utility trench: length × bucket width × depth. A 100 ft trench, 1 ft wide and 2 ft deep, is 200 ft³ — about 7.4 yd³ in the ground or 9.3 yd³ loose.
- Pond: for a bowl shape, use the full length and width with roughly half the maximum depth as a quick estimate.
Planning tips
- Call before you dig. In the US, call 811 a few days ahead to have underground utilities marked; other countries have similar services.
- Dig a little extra around foundations and footings for formwork and working space — often 1–2 ft (300–600 mm) each side.
- Slope or shore trench walls deeper than 5 ft (1.5 m); trench collapses are a leading cause of construction deaths.
- Keep good topsoil separate so you can reuse it for lawns and beds instead of paying to haul it away.
- Check disposal rules — some sites charge by weight, and contaminated soil needs special handling.