Slab dimensions in, order-ready concrete math out — cubic yards, bag counts, and delivered cost. Then send it straight into a quote.
Ballpark, not gospel. This estimates concrete volume and delivered cost from your dimensions — grade overage and pump fees are what move real concrete jobs, so confirm with your supplier before ordering.
Straight answers, no fluff. Then run your own numbers above.
Multiply length × width × thickness (in feet), divide by 27 to get cubic yards, then add 10% waste. A 20×12-foot slab at 4 inches needs about 3.3 cubic yards with waste. The calculator above runs the whole thing including the bag alternative.
Roughly 45 sixty-pound bags or 60 eighty-pound bags per cubic yard. Bags make sense under half a yard — beyond that, a ready-mix truck is cheaper per yard and far faster.
Four inches handles patios, walkways, and sheds. Driveways and slabs carrying trucks need 6 inches, and structural slabs need rebar or mesh on top of the thickness. Never go under 4 inches for anything bearing weight.
Materials run about $4–$8 per square foot for a standard 4-inch slab; installed with forming, rebar, and finishing, expect $6–$12. Ready-mix delivered averages $150–$180 per cubic yard in 2026.
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Got your yards? Turn this estimate into a professional concrete quote and send it before you leave the job site.