How much concrete for a 18×30 slab 4 inches thick?
Answer
6.67 cubic yards
251 bags of 80lb concrete mix400 bags of 60lb mixOrder ready-mix delivery (~$1,001)Add 10% for waste = 7.34 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(30 × 18 × 4/12) / 27 = 180.00 / 27 = 6.67 cubic yards
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Calculated using verified formulas. Last updated March 2026.