Concrete Calculator
Get cubic yards for a slab, footing, or column, plus 60 lb and 80 lb bag counts from an editable yield.
Smart Tips
• A slab is length × width × thickness.
• A footing uses the same product, times how many identical runs you have.
• A round column is π × radius² × height. A square column is side × side × height.
• Cubic yards are cubic feet divided by 27.
• Bag counts are cubic feet divided by the yield in the form, not rounded up.
• A thickness of 0 is 0 yards and 0 bags.
The Formula
The printed yields are approximate QUIKRETE Concrete Mix figures. Change either yield if the bag you buy says something else. A 9 ft × 3 ft × 4 in slab is 9 cubic feet, 15 of the 80 lb bags, and 20 of the 60 lb bags.
Key Insights
Geometry first
The yardage is the solid. The bags come after, by dividing by the yield.
Editable yield
0.60 and 0.45 are starting points, not a locked product choice.
Zero pour
A slab with no thickness needs no concrete and no bags.
Order check
The bag figure can be fractional. Round up yourself if you want whole bags on site.
Frequently Asked Questions
Note:Bag counts use the yields in the form. The defaults are QUIKRETE Concrete Mix product 1101: about 0.60 cubic feet per 80 lb bag and about 0.45 cubic feet per 60 lb bag. Volume is geometric, then divided by that yield.