Concrete Calculator
The Concrete Calculator estimates how many cubic yards of concrete — and how many pre-mixed bags — you need for a slab, footing, or round column.
Concrete Needed
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Cubic Feet--
60 lb Bags--
80 lb Bags--
How volume is calculated
For a rectangular slab or footing:
Volume (ft³) = Length × Width × (Thickness in inches / 12)
For a round column or tube:
Volume (ft³) = π × radius² × Height
Cubic feet is then divided by 27 to get cubic yards (the unit ready-mix concrete is typically sold in), or divided by a bag's yield to estimate bag count (a standard 60 lb bag yields about 0.45 ft³; an 80 lb bag yields about 0.6 ft³).
Example: A 10 ft × 10 ft slab poured 4 inches thick needs about 1.23 yd³ of concrete — roughly 75 bags at 60 lb each.
Ordering tip
Always order 5–10% extra concrete to account for spillage, uneven subgrade, and measurement variance. Use the Conversion Calculator if you need to convert between metric and imperial measurements first.