What this calculator actually models
Concrete quantity starts with geometric volume. A slab uses length × width × thickness; a round pier or cylinder uses π × radius² × height. The calculator then converts the result into common ordering units and can add a user-selected waste allowance.
How to use this calculator
Choose slab or cylinder.
Enter dimensions in feet; convert inches to feet when necessary (for example, 4 in = 0.3333 ft).
Add only the waste allowance appropriate to your project and supplier, then verify the volume before ordering.
Where people use it
- •Slabs, pads and small foundations
- •Round piers and posts
- •Early material planning before obtaining a supplier quote
Example: 12 ft × 10 ft × 4 in slab
4 in = 0.3333 ft. The geometric volume is about 40 cu ft, or 1.48 cu yd before any waste allowance.
Assumptions and limits
- •This calculator does not assume a bag yield because bag coverage varies by product and manufacturer. Use the yield printed on the product you will actually buy.
- •Excavation tolerances, subgrade, irregular geometry, overbreak and supplier minimums can change the ordered quantity.
Frequently asked questions
How many cubic feet are in a cubic yard?+
There are exactly 27 cubic feet in one cubic yard.
How do I enter a 4-inch slab thickness?+
Convert inches to feet by dividing by 12. Four inches is approximately 0.3333 ft.
Does this tell me how many bags to buy?+
Not automatically. Use the actual yield stated on the bag because product yields differ.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.