How much concrete for a 15×18 slab 5 inches thick?
Answer
4.17 cubic yards
157 bags of 80lb concrete mix250 bags of 60lb mixOrder ready-mix delivery (~$626)Add 10% for waste = 4.59 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(18 × 15 × 5/12) / 27 = 112.50 / 27 = 4.17 cubic yards
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Calculated using verified formulas. Last updated March 2026.