Concrete Calculator
Calculate how much concrete you need for slabs, footings, columns, and steps in cubic yards and bags.
Result
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A concrete calculator estimates how many cubic yards or bags of concrete you need for slabs, footings, columns, and other projects.
Examples
10x20 ft patio, 4 inches thick
Volume = 20 x 10 x (4/12) = 6.67 cu ft / 27 = 2.47 cu yards. With 10% waste: 2.72 cu yards.
Four 12-inch round columns, 4 feet tall
Each column = pi x 6^2 x 48 = 5,429 cu in = 0.116 cu yd. Four columns = 0.466 cu yd.
Frequently Asked Questions
How much does a cubic yard of concrete weigh?
Wet concrete weighs approximately 3,900 to 4,050 pounds per cubic yard (about 150 lbs per cubic foot).
Should I use bags or order a truck?
For projects under 1 cubic yard, pre-mixed bags are practical. For 1-3+ cubic yards, ordering from a ready-mix plant is more economical and ensures consistent quality.
Result
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Quick Tips
- •Always add 5-10% waste factor for slabs and 10-15% for complex shapes.
- •Concrete is sold by the cubic yard for truck delivery; one truck typically carries 8-10 yards.
- •Standard slab thickness is 4 inches for patios and 6 inches for driveways.
- •An 80 lb bag of pre-mix yields approximately 0.6 cubic feet of concrete.