Concrete Trench Calculator
Estimate concrete volume, bag quantity, excavation footprint, placed weight and cost for one or more straight concrete-filled trenches.
Default project preview
1.81 yd³
Concrete bags
82
Base volume
1.65 yd³
Total trench length
40 ft
Excavation footprint
53.3 ft²
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Input and output guide
What each value means
The labels and units below are part of this calculator’s visible methodology. Replace every default with measurements or product data from the actual project.
Trench length
Enter this project assumption in ft. The current imperial default is 40 ft.
Trench width
Enter this project assumption in in. The current imperial default is 16 in.
Concrete depth
Enter this project assumption in in. The current imperial default is 10 in.
Equal trenches
Enter this project assumption in a unitless value. The current imperial default is 1. Minimum: 1.
Extra allowance
Enter this project assumption in %. The current imperial default is 10 %. Minimum: 0. Maximum: 50.
Concrete yield per bag
Enter this project assumption in ft³. The current imperial default is 0.6 ft³.
Ready-mix price
Enter this project assumption in per yd³. The current imperial default is 165 per yd³. Minimum: 0.
Price per bag
Enter this project assumption in a unitless value. The current imperial default is 7. Minimum: 0.
How to read the outputs
Concrete bags
rounded full bags. Default preview: 82.
Base volume
before allowance. Default preview: 1.65 yd³.
Total trench length
all equal trenches. Default preview: 40 ft.
Excavation footprint
length × width. Default preview: 53.3 ft².
Placed weight
planning density. Default preview: 7,325 lb.
Cost comparison
ready-mix / bags. Default preview: $298.77 / $574.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Volume = trench length × width × concrete depth × quantity. The allowance is applied before converting to ready-mix volume or rounding bags up.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Estimate concrete volume for continuous strip trenches while separating excavation geometry from the concrete section actually poured.
Calculation steps
- 1Enter the actual project dimensions or operating values.
- 2Apply the calculator formula using consistent units.
- 3Review the unrounded result and the editable allowance.
- 4Round only to the product, stock length or equipment increment actually purchased.
Worked numerical example
A 40 ft trench with a 16 in × 8 in concrete section requires about 1.32 yd³ before waste.
Purchasing and rounding
Base the concrete order on the dimensions of the section that will actually be filled, not automatically on the full excavation width. Convert the final strip volume to the supplier's delivery unit and add a modest placement allowance for trench irregularity only where field conditions justify it.
Interpret the result
The result represents the continuous concrete strip defined by length, concrete width and concrete depth. If the excavation is wider than the footing, or contains steps and thickened sections, those differences must be modeled separately before ordering.
Page-specific assumptions
- Inputs describe one consistent project condition.
- Entered yields and efficiencies match the selected product or equipment.
- Site-specific code and engineering requirements are checked separately.
Common mistakes
- Mixing imperial and metric inputs.
- Using nominal dimensions where actual coverage controls.
- Rounding intermediate values too early.
- Treating a quantity estimate as design approval.
Primary and technical references
BuildMeter provides planning estimates, not engineering, architectural, electrical, mechanical, plumbing, permit or code approval. Review the methodology and verify final decisions with product documentation and qualified professionals.
FAQ
Concrete Trench Calculator questions
Should trench dimensions be measured inside the excavation?+
Use the actual concrete dimensions. Excavation may be wider where forms, working room or unstable soil are involved.
Does the calculator include a gravel base?+
No. Base aggregate and drainage materials should be estimated separately.
Can this size a foundation trench?+
No. Width, depth and reinforcement must come from an approved project design.