How much concrete for a 40×40 slab 4 inches thick?
Answer
19.75 cubic yards
741 bags of 80lb concrete mix1186 bags of 60lb mixOrder ready-mix delivery (~$2,963)Add 10% for waste = 21.73 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(40 × 40 × 4/12) / 27 = 533.33 / 27 = 19.75 cubic yards
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Calculated using verified formulas. Last updated March 2026.