Concrete Calculator
Calculate cubic yards, bags, and estimated cost for your concrete project.
Results
Volume —
40 lb bags —
60 lb bags —
80 lb bags —
Includes 10% extra for waste and spillage. Actual amounts may vary.
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How to Calculate Concrete
Concrete is sold by the cubic yard. To calculate how much you need, determine the volume of the area you're filling, then convert to cubic yards.
Slab / Patio Formula
Volume (cu yd) = (Length × Width × Thickness) / 27
Where all dimensions are in feet (convert inches to feet by dividing by 12)
Where all dimensions are in feet (convert inches to feet by dividing by 12)
Column / Post Hole Formula
Volume (cu yd) = π × (Diameter/2)² × Depth × Quantity / 27
Where diameter is converted to feet
Where diameter is converted to feet
Bag Coverage
Pre-mixed concrete bags cover the following volumes:
- 40 lb bag: 0.011 cubic yards (0.30 cu ft)
- 60 lb bag: 0.017 cubic yards (0.45 cu ft)
- 80 lb bag: 0.022 cubic yards (0.60 cu ft)
For projects over 1 cubic yard, consider ordering ready-mix concrete from a local supplier — it's typically cheaper and faster than mixing bags by hand.
Common Concrete Thicknesses
- 4 inches: Sidewalks, patios, shed floors
- 5-6 inches: Driveways, garage floors
- 8-12 inches: Footings, foundation walls
Tips for Ordering Concrete
- Always order 10% extra to account for waste, spillage, and uneven subgrade
- For colored or stamped concrete, order all material at once for color consistency
- Ready-mix concrete starts at about $100-150 per cubic yard depending on your location
- Standard concrete strength for residential is 3,000-4,000 PSI
- For DIY slab projects, consider getting a concrete mixer to save time and effort
- A sturdy wheelbarrow makes transporting bags and mixed concrete much easier