Trench Calculator
Calculate the volume of a trench excavation.
Last updated 2026-08-21
What Is a Trench Calculator?
A trench calculator works out the volume of soil removed for a narrow, long excavation like a utility or drainage trench. You enter the trench length, width, and depth. The result in cubic yards tells you how much to haul and how much backfill to order.
How It Works
Volume = Trench Length × Width × Depth. Cubic yards = Volume ÷ 27.
Example
A 50 ft × 2 ft × 4 ft trench is 400 cu ft = 14.8 cubic yards.
How to Calculate
- Measure the trench length, width, and depth in feet. A 50 ft long, 2 ft wide, 4 ft deep trench is 400 cubic feet.
- Divide by 27 to convert to cubic yards, giving 14.8 cubic yards.
- Set the width to the pipe or utility width plus working room, often 12 to 24 inches.
- If the trench is sloped or shored, use the average width because the top is wider than the bottom.
- Note that this total includes the space for pipe, bedding, and backfill, not just the backfill itself.
Typical Trench Widths by Use
| Trench Use | Typical Width (in) | Typical Depth (ft) |
|---|---|---|
| Residential water line | 12 to 18 | 3 to 5 |
| Sewer / septic line | 18 to 24 | 4 to 6 |
| Electrical conduit | 12 to 16 | 2 to 4 |
| Drainage / French drain | 12 to 18 | 1 to 3 |
| Storm culvert | 24 to 36 | 3 to 6 |
Sources
Frequently Asked Questions
What trench width should I use?
Trench width is usually the pipe or utility width plus working room — often 12–24 in.
Should I account for sloping?
Shored or sloped trenches have wider tops, so use the average width in that case.
Is this the same as pipe bed volume?
No — the trench holds pipe, bedding, and backfill. This tool gives the total excavated volume.
Estimate the cost with the Excavation Cost Calculator or browse Excavation Calculators