Concrete Calculator

Pouring a patio slab, a set of structural columns, or foundation footings means committing to a concrete order before the truck arrives, and getting that number wrong costs money in either direction. The figure that matters is cubic yards. Ordering short stalls the job; ordering long pays for material that hardens in the chute.

Each shape has its own volume formula. A slab (or a rectangular footing) is Length x Width x Depth, with the depth entered in inches; a round column is Pi x (Radius)^2 x Height, with the diameter entered in inches. There is also a stairs option. The calculator converts everything to feet, multiplies by the quantity, adds a 10% waste allowance and divides by 27 to get cubic yards, shown to two decimals. It also counts 80-lb bags at 0.60 cubic feet each, the yield Quikrete lists for its Concrete Mix, prices the volume at $150 per cubic yard, and gives the weight at 150 lbs per cubic foot.

The 10% allowance is already in the total; add more when the forms are intricate or the subgrade sits unevenly. The errors that bite hardest are an understated slab thickness or a miscalled column diameter, both of which leave you short mid-pour. Keep every measurement in the same unit, all feet or all inches, and convert only once, because mixing units is where the largest mistakes creep in.