Concrete Calculator
Calculate cubic yards of concrete needed for any slab.
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How It Works
Calculates concrete volume in cubic yards for a rectangular pour: Volume = Length × Width × Depth ÷ 27 (cubic feet per yard). Always add 10% for waste and spillage.
Formula
Volume = L x W x DQuick Reference
Common calculations — results you can verify instantly.
10×10ft patio, 4in
10×10×(4/12)/27
1.23 cu yd
Driveway 20×30ft, 4in
20×30×(4/12)/27
7.41 cu yd
One bag 80lb
Coverage
0.6 cu ft (60 bags/cu yd)
Tips & Shortcuts
Order 10% extra concrete to account for waste.
A standard driveway (20×20ft, 4in deep) needs ~5 cubic yards.
Concrete is ordered in cubic yards from ready-mix companies.
Common Mistakes
Forgetting to convert inches to feet for depth
Depth in inches ÷ 12 = depth in feet. 4 inches = 0.333 feet.
Ordering exactly calculated amount with no buffer
Always add 10% buffer. Running out mid-pour is a serious problem — concrete cannot wait.
Frequently Asked Questions
10 × 10 × (4/12) = 33.3 cubic feet ÷ 27 = 1.23 cubic yards. Order 1.4 cubic yards with 10% buffer.
An 80-lb bag yields ~0.6 cubic feet. You need ~60 bags per cubic yard (very labor-intensive — order ready-mix for larger pours).
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