Concrete for a 16×20 Slab at 4" Thick
A 16 ft × 20 ft slab poured 4 inches thick is 320 sq ft and needs 3.95 cubic yards of concrete — order 4.27 CY to cover 8% waste, or about 192 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.