How much concrete for a 18×36 slab 6 inches thick?
Answer
12.00 cubic yards
450 bags of 80lb concrete mix720 bags of 60lb mixOrder ready-mix delivery (~$1,800)Add 10% for waste = 13.20 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(36 × 18 × 6/12) / 27 = 324.00 / 27 = 12.00 cubic yards
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Calculated using verified formulas. Last updated March 2026.