Trench/Ditch Volume Calculator
Calculate cubic yards or cubic meters of material to remove or fill in a trench or ditch.
Enter length, width, and depth for accurate excavation estimates.
Ditch excavation volume calculation is fundamental for drainage channels, irrigation ditches, utility trenches, and foundation perimeters. The cross-section of a ditch is rarely a simple rectangle — side slopes (batters) are used for soil stability, creating a trapezoidal cross-section.
Trapezoidal cross-section volume formula:
Cross-Section Area = (Top Width + Bottom Width) ÷ 2 × Depth
Volume = Cross-Section Area × Length
Side slope (batter) calculation: A slope expressed as H:V (horizontal : vertical) means for every 1 unit of depth, the bank extends H units outward.
Top Width = Bottom Width + (2 × Depth × Slope Ratio)
Common side slopes by soil type:
| Soil Type | Minimum Slope Ratio (H:V) |
|---|---|
| Rock | 0.25:1 |
| Firm clay | 0.5:1 |
| Sandy clay | 1:1 |
| Loose sand | 1.5:1 |
| Wet or loose soil | 2:1 |
Worked example: An irrigation ditch, 200 meters long, 0.8 m deep, 0.5 m bottom width, in sandy clay (1:1 slope):
- Top width: 0.5 + (2 × 0.8 × 1) = 0.5 + 1.6 = 2.1 m
- Cross-section area: (2.1 + 0.5) ÷ 2 × 0.8 = 1.04 m²
- Volume: 1.04 × 200 = 208 m³ of excavation
- At 1.35 t/m³ (sandy clay bulk density): 280.8 tonnes of spoil to remove
Cost estimation:
- Small excavator: $100–$200/hour, producing ~40–80 m³/hour
- 208 m³ ÷ 60 m³/hr = ~3.5 machine hours → $350–$700 excavation cost
- Spoil disposal (if offsite): add $10–$25 per tonne
Dewatering note: If the ditch bottom will be below the water table, budget for pump-out during and after excavation.