Concrete for a 20×24 Slab at 4" Thick
A 20 ft × 24 ft slab poured 4 inches thick is 480 sq ft and needs 5.93 cubic yards of concrete — order 6.40 CY to cover 8% waste, or about 289 80-lb bags for a small pour. Adjust the dimensions below for your project.
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Want the full guide — tools, step-by-step, common mistakes and FAQ? See the Concrete Slab Calculator.