Trench Calculator
A 40 by 2 by 3 foot trench, 30 percent swell, and 6 inches of bedding hauls 4.15 loose cubic yards when the native soil goes back.
Last updated . Swell starts at 30 percent, the high end of the loam planning range. Bedding starts at 0.5 ft. The truck starts at 10 cubic yards.
Bank cut is length × width × depth. The loose pile applies swell. Spoil is what will not fit after native soil goes back above the bedding.
Soil weight at 1,400 kg/m³: backfill calculator. Drain stone around a pipe: French drain calculator. Stone size, fabric, and bedding for that drain are the French drain gravel guide.
Trench cut and backfill
Bedding is imported material in the bottom of the trench, at the depth you type. The rest can go back as native soil. Spoil to haul is the swell that will not fit, plus the space the bedding takes. Swell starts at the high end of a planning range. This is not gravel in a French drain and it is not a weight at 1,400 kg/m³.
Results
How the cut and the split are calculated
Forty feet by 2 feet by 3 feet is 240 cubic feet, 8.89 bank cubic yards, 6.80 m³. At 30 percent swell the loose pile is 11.56 yd³ · 8.83 m³. Bedding of 0.5 ft is 1.48 yd³ · 1.13 m³. Native soil fills the rest, 7.41 yd³ · 5.66 m³. Spoil to haul is 4.15 yd³ · 3.17 m³, one 10 yard truck.
That spoil is the swell, 2.67 yards, plus the bedding, 1.48 yards. Uncheck native soil and the whole 11.56 yard pile is haul, 2 loads. A French drain’s stone and the backfill page’s tons are different jobs. Swell ranges match the excavation page and are planning figures, not a soil test.
The same 40 by 2 by 3 trench
Truck capacity stays 10 yd³. Swell is 30 percent unless the row says otherwise.
| Case | Native backfill | Spoil | Loads |
|---|---|---|---|
| 0.5 ft bedding, soil put back | 7.41 yd³ | 4.15 yd³ | 1 |
| No bedding, soil put back | 8.89 yd³ | 2.67 yd³ | 1 |
| 0.5 ft bedding, haul everything | 0.00 yd³ | 11.56 yd³ | 2 |
| 0.5 ft bedding, 0% swell | 7.41 yd³ | 1.48 yd³ | 1 |
Worked example
Enter 40 ft, 2 ft, and 3 ft. Leave bedding at 0.5 ft, swell at 30, the truck at 10 yd³, and native soil checked. Bank reads 8.89 yd³ · 6.80 m³. Spoil to haul reads 4.15 yd³ · 3.17 m³. Truck loads read 1.
Trench questions
How much spoil comes out of a 40 foot trench?
Leave 40 ft long, 2 ft wide, and 3 ft deep. Bedding stays 0.5 ft. Swell stays 30. Native soil stays checked. Bank reads 8.89 yd³ · 6.80 m³. Loose pile reads 11.56 yd³ · 8.83 m³. Imported bedding reads 1.48 yd³ · 1.13 m³. Native backfill reads 7.41 yd³ · 5.66 m³. Spoil to haul reads 4.15 yd³ · 3.17 m³. Truck loads read 1.
Why is the haul smaller than the loose pile?
The loose pile is the whole cut after swell, 11.56 cubic yards. Native soil put back fills 7.41 cubic yards of the hole. What will not fit is the 30 percent swell plus the 1.48 yards the bedding displaces, 4.15 cubic yards. Spoil = bank × swell ÷ 100 + bedding.
What if none of the native soil goes back?
Uncheck Put native soil back above the bedding. Native backfill reads 0.00 yd³ · 0.00 m³. Spoil to haul matches the loose pile, 11.56 yd³ · 8.83 m³. Truck loads read 2. Imported bedding still reads 1.48 yd³ · 1.13 m³. Bank stays 8.89 yd³ · 6.80 m³.
What if there is no imported bedding?
Check native soil again and set bedding depth to 0. Imported bedding reads 0.00 yd³ · 0.00 m³. Native backfill reads 8.89 yd³ · 6.80 m³. Spoil to haul reads 2.67 yd³ · 2.04 m³, which is only the swell. Truck loads read 1.
What if swell is zero?
Set swell to 0 and bedding back to 0.5 ft, with native soil checked. Loose pile matches the bank, 8.89 yd³ · 6.80 m³. Spoil to haul reads 1.48 yd³ · 1.13 m³, the bedding space only. Truck loads read 1. Nothing extra comes from swell.
Does a 2 foot depth match the backfill page?
Set depth to 2 ft, bedding to 0, and swell to 0, with native soil checked. Bank reads 5.93 yd³ · 4.53 m³. That is the same hole as the backfill page’s 40 foot by 2 foot by 2 foot example. Spoil to haul reads 0.00 yd³ · 0.00 m³ and truck loads read 0, because the soil goes back and it did not swell. The backfill page then weighs that 5.93 yards at 1,400 kg/m³. This page does not.
Is this a French drain?
No. Stone around a pipe, with the pipe subtracted, is the French drain calculator. Sand in a trench is the trench sand calculator. Weight of soil put back at 1,400 kg/m³ is the backfill calculator. This page is the cut, the swell, the bedding split, and the spoil loads.