Concrete Beam Calculator
Estimate concrete volume, full bag quantity, form-contact area, placed weight and ready-mix cost for identical rectangular concrete beams.
Default project preview
2.44 yd³
Concrete bags
110
Base volume
2.22 yd³
Total beam length
40 ft
Three-face forms
160 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.
Beam length
Enter this project assumption in ft. The current imperial default is 20 ft.
Beam width
Enter this project assumption in in. The current imperial default is 12 in.
Beam depth
Enter this project assumption in in. The current imperial default is 18 in.
Equal beams
Enter this project assumption in a unitless value. The current imperial default is 2. 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: 110.
Base volume
before allowance. Default preview: 2.22 yd³.
Total beam length
all identical beams. Default preview: 40 ft.
Three-face forms
bottom and two sides. Default preview: 160 ft².
Placed weight
planning density. Default preview: 9,889 lb.
Cost comparison
ready-mix / bags. Default preview: $403.33 / $770.00.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Beam volume = length × width × depth × quantity. The allowance is applied before concrete bags and ready-mix volume are rounded.
Reviewed project guidance
How to use this estimate in a real project
Last reviewed: July 30, 2026
Use this calculator to estimate concrete volume for one or more rectangular beams from length, width and depth. It supports material ordering only and does not determine beam size, reinforcement, bearing or structural capacity.
Calculation steps
- 1Convert width and depth to consistent units.
- 2Calculate one beam as length × width × depth.
- 3Multiply by beam quantity.
- 4Add placement allowance and convert to supplier units.
Worked numerical example
A beam 20 ft long × 12 in wide × 18 in deep has 30 ft³, or 1.11 yd³. Three equal beams require 3.33 yd³ before allowance.
Purchasing and rounding
Ready-mix is ordered in supplier increments. Include pump-line, form leakage and contingency appropriate to the placement.
Interpret the result
Beam depth and width both scale volume linearly. Multiple beams should be separated when their dimensions differ.
Page-specific assumptions
- Rectangular uniform section.
- Equal beams unless calculated separately.
- No haunches or corbels.
- Reinforcement volume is not deducted.
Common mistakes
- Leaving inches unconverted.
- Combining unequal beams with one average.
- Ignoring haunches.
- Treating quantity output as structural 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 Beam Calculator questions
Does this calculator size a structural beam?+
No. Structural beam dimensions and reinforcement depend on loads, spans, supports, materials and code.
What form area is included?+
The estimate includes the beam bottom and two long sides, but not end caps, supports or waste.
Should beam concrete include extra material?+
A modest allowance can cover form variation and handling loss, but confirm large pours with the supplier.