How the trench calculator works
Utility lines, footings, drains, and irrigation runs all start with a trench, and the answer tells you how much soil comes out or how much fill goes back in.
Use this cubic yard calculator for a trench to get cubic yards, cubic feet, cubic meters, and a cost estimate in one step.
The calculator multiplies out the volume in cubic feet, then divides by 27, because a cubic yard is a cube that is 3 feet on each side. For this shape the formula is shown below in words and symbols.
In plain words: length times width times depth, then divide by 27 if your answer is in cubic feet. Mixed units are fine. Pick feet, inches, yards, meters, or centimeters next to each box and the tool converts them for you.
Worked example for a trench
Take a trench with length 50 ft, width 12 in, depth 18 in. The volume works out to 75.00 cubic feet. Divide by 27 and you get 2.78 cubic yards. With 10 percent extra for waste, order about 3.06 cubic yards.
Measuring a trench
Measure the full length of the trench, the width at the bottom, and the depth. Use inches for width and depth on narrow trenches.
Common uses for the trench calculator
- French drains and drain pipe trenches
- Concrete footings
- Utility and irrigation trenches
- Gravel filled drainage trenches
Trench volume at different sizes
The table scales the example above so you can see how fast volume grows. Doubling the depth doubles the volume. Doubling every length quadruples the area, and with the same depth the volume quadruples too.
| Size | Cubic feet | Cubic yards | With 10 percent extra |
|---|---|---|---|
| 25 ft by 6 in by 18 in | 18.75 | 0.69 | 0.76 |
| 50 ft by 12 in by 18 in | 75.00 | 2.78 | 3.06 |
| 75 ft by 18 in by 18 in | 168.75 | 6.25 | 6.88 |
| 100 ft by 24 in by 18 in | 300.00 | 11.11 | 12.22 |
| 150 ft by 36 in by 18 in | 675.00 | 25.00 | 27.50 |
| 50 ft by 12 in by 36 in | 150.00 | 5.56 | 6.11 |
| 100 ft by 24 in by 36 in | 600.00 | 22.22 | 24.44 |
What the 2.78 cubic yard example weighs
Volume is only half of the story when a truck is hauling the load. The table shows planning weights for the example volume in several materials.
| Material | US tons | Pounds |
|---|---|---|
| Topsoil | 3.06 | 6,111 |
| Mulch | 0.97 | 1,944 |
| Gravel | 3.89 | 7,778 |
| Sand | 3.75 | 7,500 |
| Concrete | 5.62 | 11,250 |
| Compost | 1.39 | 2,778 |
These figures are planning estimates. Real material varies in moisture, size, and compaction, so confirm weights and order quantities with your supplier.
Frequently asked questions
How do I calculate cubic yards for a trench?
Find the volume in cubic feet, then divide by 27. For this shape: length times width times depth. Convert inches to feet first by dividing by 12.
How many cubic yards is the example trench?
Length 50 ft, width 12 in, depth 18 in comes to 2.78 cubic yards, or 75.00 cubic feet.
How much extra should I order?
Most people add 5 to 10 percent for waste, and 10 to 15 percent for rough ground or loose material.
Can I use metric units?
Yes. Choose meters or centimeters next to any length. The result still shows cubic yards, and the cubic meter figure sits beside it.
Why does the answer change with the material?
The volume does not change, but weight and bag counts do, because each material has a different density.