Concrete calculator
Calculate cubic yards, number of bags, and estimated cost for slabs, footings, and columns.
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Concrete is ordered in cubic yards. One cubic yard equals 27 cubic feet and covers about 80 square feet at 4 inches thick. For small projects, premixed bags are more practical — a 60 lb bag yields about 0.45 cubic feet, and an 80 lb bag yields about 0.6 cubic feet.
Tips
- Order 5-10% extra to account for waste, uneven subgrade, and form irregularities
- Standard slab thickness is 4" for patios and walkways, 6" for driveways
- Footings are typically 8-12" deep and twice the width of the wall they support
- Sonotube columns are common at 8", 10", and 12" diameters
How many bags of concrete do I need for a 10x10 slab?
A 10'x10' slab at 4" thick requires about 1.24 cubic yards or approximately 56 bags of 60 lb mix. At 6" thick, you'd need about 1.85 cubic yards or 83 bags.
FAQ
How many bags of concrete are in a cubic yard?
A cubic yard equals 27 cubic feet. An 80-lb bag covers about 0.6 cubic feet, so you need approximately 45 bags of 80-lb concrete per cubic yard. A 60-lb bag covers about 0.45 cubic feet, requiring roughly 60 bags per yard.
How thick should a concrete slab be?
Standard garage slabs and driveways are 4 inches thick. Patios and walkways can be 3.5 to 4 inches. Heavy vehicle areas like RV pads should be 5 to 6 inches. Always check local code requirements.
Should I add extra concrete for waste?
Yes. Order 5-10% extra for standard pours to account for uneven subgrade, spillage, and form variations. For irregular shapes or sloped sites, add 10-15% extra.