Concrete Calculator
Estimate concrete volume, ready-mix yards, and bag quantities for rectangular or circular projects.
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How this calculator works
Rectangle volume = length × width × depth. Circle volume = π × (diameter ÷ 2)² × depth. Cubic yards = cubic feet ÷ 27, then the waste allowance is added.
Worked example
A 12 × 10 ft rectangular pour at 4 in deep with 10% extra requires about 1.63 cubic yards.
Sources & assumptions
Bag estimates use approximate yields of 0.45 ft³ for a 60-lb bag and 0.60 ft³ for an 80-lb bag, consistent with QUIKRETE Concrete Mix product data. Product labels and site conditions control.
Frequently asked questions
How much extra concrete should I order?
Five to ten percent is a common planning allowance for grade variation, spillage, and measurement error.
How many bags equal a cubic yard?
Yield varies by product. Using common planning yields, one cubic yard is about 60 60-lb bags or 45 80-lb bags. Check the bag label.
Concrete slab guide
Planning a small slab? See the full worked example, bag counts, and thickness table in How much concrete for a 10×10 slab?