Excavation Volume Calculator

Excavation quantities drive earthwork costs, equipment planning and the number of truck loads to haul away. This calculator works out the in-place (bank) volume of trenches, pits and foundation excavations, converts it to loose volume using a swell factor, and estimates truck trips.

How to use it

1. Choose the shape, such as a rectangular pit or trench.
2. Enter length, width and depth, plus side slope if the sides are battered.
3. Enter the swell factor for the soil and the truck capacity.
4. Read bank volume, loose volume and the number of loads.

Formulas

• Vertical sides: V = L × W × D
• Sloped sides (prismoidal): V = D / 6 × (A1 + 4Am + A2), where A1 is the bottom area, A2 the top area and Am the area at mid-depth.
• Loose volume = bank volume × swell factor.

Worked example

A foundation pit with a 10 m × 8 m base, 2 m deep and side slopes of 1:1 has a top of 14 m × 12 m. Bottom area = 80 m², top area = 168 m², mid-depth area (12 m × 10 m) = 120 m². Volume = 2 / 6 × (80 + 480 + 168) = 242.7 m³ bank. With a swell factor of 1.25, loose volume = 303 m³, which is about 31 trips for a 10 m³ truck.

Typical swell factors

• Sand and gravel: 1.10 to 1.15
• Common earth: 1.20 to 1.30
• Clay: 1.30 to 1.40
• Blasted rock: 1.50 to 1.70

Site notes

Allow working space around foundations, follow safe slope or shoring requirements for trench depths over about 1.5 m, and keep spoil heaps back from the edge.