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.
Concrete needed
5.93 cu yd
Slab area
480 sq ft
Concrete needed
5.93 cubic yards6.40 CY with 8% waste — order this much
80-lb bags
289 bagsor 384 × 60-lb bags
Ready-mix cost (est.)
$1,120~$175/CY delivered
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How this is calculated
Concrete volume = area × thickness. We convert to cubic yards (the unit ready-mix is sold in), then add 8% for spillage and over-ordering — the same waste factor used in professional estimating.