How much concrete for a 20×20 slab 4 inches thick?
Answer
4.94 cubic yards
186 bags of 80lb concrete mix297 bags of 60lb mixOrder ready-mix delivery (~$741)Add 10% for waste = 5.43 cy
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How We Calculated This
Cubic yards = (L × W × D/12) / 27
(20 × 20 × 4/12) / 27 = 133.33 / 27 = 4.94 cubic yards
Related Calculations
How much concrete for a 4×4 slab 4 inches thick?0.20 cubic yardsHow much concrete for a 4×4 slab 6 inches thick?0.30 cubic yardsHow much concrete for a 4×4 slab 8 inches thick?0.40 cubic yardsHow much concrete for a 4×6 slab 4 inches thick?0.30 cubic yardsHow much concrete for a 4×6 slab 6 inches thick?0.44 cubic yards
Calculated using verified formulas. Last updated March 2026.