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.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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