Free tool
Trench volume calculator
Excavation, bedding, and backfill in cubic yards for a single pipe run — the same math BidSheet's Trench Profiler uses. Enter your dimensions; everything updates as you type. Runs entirely in your browser, no signup.
Estimates for planning only — verify against your geotech, trench-safety plan, and local spec before bidding or digging. Bench width models a benched/sloped wall on each side; use 0 for shored vertical walls.
How it's calculated
How the volumes are calculated
Fall & depth. Fall over the run is grade% ÷ 100 × run length.
End depth is start depth + fall, and the trench volume uses the average of the two
(average-end-area), so a 4 ft start on a 2% / 100 LF run averages 5 ft deep.
Excavation. (trench width + 2 × bench width) × average depth × run length ÷ 27
for cubic yards. Bench width is added to each side.
Bedding. trench width × bedding depth × run length ÷ 27 —
a full-width layer under the pipe (benches excluded).
Backfill. Excavation minus bedding minus the pipe's own volume
(treated as a cylinder, π × r² × pipe length). Subtracting the whole pipe is
deliberately conservative and stays within takeoff tolerance.
Pipe length & tracer wire follow the slope (the hypotenuse of run and fall), so they run slightly longer than the horizontal length; warning tape runs the horizontal length.
Why grade can't be negative
Enter every run from its upstream (shallow) end so the pipe always falls downstream. A "rising" run is just the same trench measured from the other end — flip your start and end, and the grade is positive again.
What's the spoil number?
Excavated dirt swells when you dig it. The spoil figure applies a typical 1.25 swell (bulking) factor to excavation volume as a rough haul-off / stockpile estimate. Real swell varies a lot by soil — sand is lower, clay is higher — so treat it as a ballpark.
This is one run. Your bid has dozens.
BidSheet does this for every run in a job, rolls the trench quantities into your bid proposal alongside pipe, fittings, and crew costs, and keeps the whole estimate on your computer. Free, open source, no account.
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