Concrete beam quantity guide
Beam volume is length multiplied by finished width and height. Repeated identical beams can be combined before allowance.
Use dimensions from approved project documents; this calculator does not design the beam or reinforcement.
How to estimate concrete for rectangular beams
- Choose units: Enter all dimensions in the displayed units.
- Enter finished geometry: Use concrete dimensions rather than excavation or form dimensions.
- Count identical beams: Run separate calculations when dimensions differ.
- Review allowance: Set an allowance appropriate to placement conditions and supplier rules.
Formula and variables
Dimensions are converted to a consistent cubic unit before allowance is applied.
Volume = length × width × height × beam count- L — Length
- Finished beam length.
- W — Width
- Finished beam width.
- H — Height
- Finished beam height.
Worked example: 20-foot beam
One beam is 20 ft long, 12 in wide and 12 in high.
- Dimensions
- 20 ft × 12 in × 12 in
- Volume = 20 cubic feet.
- 20 ÷ 27 = 0.741 cubic yards.
- A 5% allowance gives 0.778 cubic yards.
Result: Plan approximately 0.78 yd³ before supplier rounding.
Confirm minimum orders and whether the beam is poured with other components.
Understanding your results
Net beam volume
Geometric volume before allowance.
Concrete to order
Net volume plus the entered allowance.
Bag equivalent
Planning comparison using the entered cubic-foot yield.
Assumptions
- Beams are rectangular and identical.
- Entered dimensions are finished concrete dimensions.
Limitations
- Haunches, slopes and penetrations are excluded.
- Structural design and reinforcement are outside scope.
Common mistakes
- Entering inches as feet.
- Using excavation dimensions.
- Treating bag yield as universal.
Practical use cases
Beam takeoff
Estimate repeated rectangular grade beams or lintels.
Order comparison
Compare ready-mix volume with packaged-concrete yield.
Planning and decision guide
Coordinate the pour
Verify forms, reinforcement, access, placement rate, testing and curing.
Confirm product yield
Use the current bag label or supplier documentation.
Frequently asked questions
Can this calculate sloped beams?
No. Divide varying geometry into suitable shapes or use a detailed takeoff.
Does it design reinforcement?
No. Use approved structural documents.
Why add allowance?
Allowance can address placement loss and quantity uncertainty, but should be project-specific.
Sources and review
- Concrete Fundamentals — American Concrete Institute. Accessed 2026-08-03.
Reviewed 2026-08-03.