Concrete Slab Calculator
Calculate the concrete volume and number of ready-mix bags needed for a slab, patio or footing.
Concrete needed
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In cubic feet —
Bags needed —
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How it works
Cubic yards = length × width × thickness (ft) ÷ 27Frequently Asked Questions
How much concrete do I need for a slab?
Multiply length × width × thickness in feet, then divide by 27 to convert cubic feet to cubic yards: a 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards.
How many bags of concrete equal a cubic yard?
About 45 bags of the standard 60 lb mix, or 60 bags of 40 lb mix, or roughly 30 bags of 80 lb mix. Bagged concrete is convenient for small jobs; ready-mix delivery is far more economical beyond about 1 cubic yard.
How thick should a concrete slab be?
4 inches for a standard patio or walkway, 5–6 inches for a driveway carrying vehicles, thicker still for heavy equipment. Always add reinforcement (rebar or mesh) for anything beyond a small non-structural pad.