Concrete Calculator
Calculate concrete volume in cubic yards and estimated cost.
Project details
Enter your measurements below.
Calculate concrete volume from slab dimensions
This Concrete Calculator converts project length, width and thickness into a concrete volume, adds the waste allowance you choose, and estimates cost from the price per cubic unit. In US mode the final purchase volume is shown in cubic yards; in Metric mode it is shown in cubic metres.
Rectangular slabs, pads and other simple concrete pours with a consistent thickness.
Concrete volume in cubic yards or cubic metres, plus estimated material cost.
The entered thickness is uniform across the full length and width.
How to use the Concrete Calculator
- Enter the slab or pad length and width.
- Enter the concrete thickness using inches in US mode or centimetres in Metric mode.
- Set a waste allowance for grade variation, spillage and small measurement differences.
- Enter your local ready-mix price per cubic yard or cubic metre if you want a cost estimate.
- For footings, columns or bagged concrete, use the dedicated calculator because the geometry or purchasing unit is different.
Formula used by DIYGauge
What this result helps you decide
Use the cubic quantity for ready-mix planning across slabs, pads or other rectangular placements.
Worked example: 12 ft × 12 ft slab, 4 in thick
- Length
- 12 ft
- Width
- 12 ft
- Thickness
- 4 in
- Waste
- 5%
- Price
- $145/cu yd
The slab contains 48 cu ft before waste, equal to about 1.78 cu yd. With 5% waste, the calculator returns about 1.87 cu yd. At $145 per cubic yard, the estimated concrete cost is about $270.67.
Practical planning tips
Actual subgrade variation can change the volume more than the mathematical slab dimensions suggest.
Ready-mix suppliers may have minimum loads, short-load fees, delivery charges or ordering increments that are separate from the concrete volume.
Structural thickness, reinforcement and concrete specification should come from the project requirements—not from the calculator.
Common mistakes to avoid
Separate non-rectangular or thickened sections and add their volumes.
Confirm whether the supplier sells by cubic yard/metre and has a minimum order.
Concrete Calculator FAQs
Why does the calculator add waste?+
A small allowance can help cover uneven excavation, spillage and measurement variation. The percentage is adjustable so you can match the job.
Is a cubic yard the same as 27 cubic feet?+
Yes. One cubic yard contains 27 cubic feet, which is why US slab volume is converted from cubic feet by dividing by 27.
Can I calculate bagged concrete here?+
Use the Concrete Bag Calculator instead. Bagged mixes are purchased by bag yield rather than by ready-mix cubic-yard volume.
Does this tell me the correct slab thickness?+
No. The calculator estimates quantity from the thickness you enter. Required thickness depends on the project, loads, site conditions and applicable requirements.
How Much Concrete Do I Need?
A step-by-step way to calculate slab volume, convert cubic feet to cubic yards and add a practical ordering allowance.