How much concrete for a 20×30 slab 5 inches thick?
Answer
9.26 cubic yards
348 bags of 80lb concrete mix556 bags of 60lb mixOrder ready-mix delivery (~$1,389)Add 10% for waste = 10.19 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(30 × 20 × 5/12) / 27 = 250.00 / 27 = 9.26 cubic yards
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Calculated using verified formulas. Last updated March 2026.