Construction & Home Improvement
Concrete Calculator
Estimate the concrete needed for a rectangular slab, patio, pad, or similar pour. Results show common volume units and a clearly labeled 80 lb bag estimate.
Rectangular slab estimate
Enter finished dimensions. The estimate includes an optional material allowance.
Estimated concrete
1.36 cubic yards
- Cubic feet
- 36.67 cu ft
- Cubic meters
- 1.04 m³
- 80 lb mix estimate
- 62 bags
How this estimate works
For a rectangular slab, volume is calculated as volume = length × width × thickness. The calculator converts each dimension to meters internally, applies your material allowance, and then reports cubic yards, cubic feet, cubic meters, and an approximate 80 lb bag count.
Example: a 10 ft × 10 ft slab at 4 in thick requires about 1.23 cubic yards before waste. With a 10% allowance, the estimate becomes about 1.36 cubic yards.
Method & sources
All dimensions are normalized using standard unit conversions. The bag estimate rounds up so that the result does not understate the number of 80 lb bags required by the selected product-yield assumption.
Important limits
- This is a material-volume estimate for a rectangular slab, not a structural design.
- Thickness, reinforcement, joint layout, and local code requirements must follow project documents and qualified local guidance.
- The 80 lb bag quantity uses a QUIKRETE product yield and may differ for other products or site conditions.
Reviewed references
- National Institute of Standards and Technology: Revised Unit Conversion Factors
Reviewed 2026-07-20. International foot conversion of 0.3048 meters and the related customary-unit conversion basis used by this calculator.
- QUIKRETE: Concrete Mix Technical Data
Reviewed 2026-07-20. Approximate 0.60 cubic foot yield for one 80 lb bag of QUIKRETE Concrete Mix. This is a product-specific estimate, not a universal bag yield.
- American Concrete Institute: Residential Concrete
Reviewed 2026-07-20. Professional residential concrete guidance used to define the calculator boundary: material estimates do not replace code, engineering, or project specifications.