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'Tips' on Ordering Your Concrete

Calculating the amount concrete of a rectangle

Length * Width * Depth / 27 = Cubic Yards 
I usually add 10% to my order so I don't run short   

To calculate concrete for patio that is 10 ft x 10 ft and 5 inches thick
Divide the number of inches 5 by 12
5 / 12 = .42 hold that number
Calculate the area: 10' * 10' = 100 sq ft 
Now calculate cubic feet: 100 * .42 =  42 
Now calculate cubic yards: 42 / 27 = 1.6 cubic yards
So I don't run short now add 10%: 1.6 * 1.1 = 1.76 cubic yards  

To calculate concrete for patio that is 10 ft x 10 ft and 4 inches thick   
10' * 10' = 100 sq ft 
100 * .33 =  33 cu. ft. 
33 / 27 = 1.2 cubic yards
1.2 * 1.1 = 1.32 cubic yards 

 

Calculating the amount concrete of a cylinder

    I use 3.14 for pi

To calculate the amount of concrete for hole 8" wide and 36 " deep the formula would be
Volume =  pi * (r * r) * Height 
Volume =  3.14 * (4" * 4") * 36" 
Volume = 3.14 * 16" * 36"
Volume = 50.24 * 36"
Volume = 1,808.64 cubic inches
Convert to cubic feet
 1,808.64 / 1,728 = 1.047 cu. ft.
Volume = 1.047 cubic feet
Convert to cubic yard
 1.047 / 27 = 0.039 cu. yd. 
Convert to 60lb bags concrete
0.039 * 3600 = 140.4
140.4 / 60 = 2.34 60lb bags concrete

For 80lb bags the calculation would be
140.4 / 80 =1.75 80lb bags concrete

More information about calculating bag in at the bottom of the page
   

 

 

Things to remember about the ordering of concrete

Different method of buying concrete

            Multiply by 3600 by the decimal of your yardage - 1/4 yd = .25
                3600 * .25 = 900 
            divide the answer by the weight of the bag
                900 / 90 = 10  bags
            If the bags weighed 65 lbs
                900 / 65 = 13.8 bags

If you have a question about anything dealing with what I have covered on this page or questions about concrete in general, please feel free to contact me by email


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