Trench Excavation Volume Calculator
Calculate the volume of soil to be excavated for a trench. Supports vertical walls and sloped (battered) sides. Results include net trench volume, spoil pile estimate, and truck load count.
Formulas Used
Width at Top: Wtop = Wbottom + 2 × S × D
Cross-Section Area (Trapezoid): A = D × (Wbottom + Wtop) / 2
Trench Volume (Bank Measure): V = L × A
Spoil Volume (Bulked): Vspoil = V × (1 + Swell% / 100)
Truck Loads: n = ⌈ Vspoil / Truck Capacity ⌉
Wall Surface Area: Awall = 2 × L × √(D² + (S·D)²) + 2 × A
Where: L = length, D = depth, S = horizontal-to-vertical slope ratio (e.g. 0.5 means 0.5 m horizontal per 1 m vertical).
Assumptions & References
- The trench has a uniform trapezoidal cross-section along its entire length.
- Side slope S is the H:V ratio applied equally to both sides of the trench.
- S = 0 represents vertical walls (rectangular cross-section).
- Bank measure volume is the in-situ soil volume before excavation.
- Swell factor accounts for soil loosening after excavation. Typical values: sand 10–15%, clay 20–30%, rock 30–40%.
- Default swell factor of 25% is a conservative general estimate (AS 3798, OSHA soil classification guidance).
- Truck loads are rounded up to the nearest whole load.
- Wall surface area is useful for estimating shoring, formwork, or pipe bedding lining requirements.
- No allowance is made for over-excavation, groundwater, or compaction of backfill.
- Reference: Nunnally, S.W. — Construction Methods and Management, 8th ed.