Online calculators and tables are helpful.
But those calculators are often tied to specific brands.
After that, figure out how many bags of dry concrete you oughta fill that space.
The Spruce / Michela Buttignol
Using the example of pouring a long, narrowconcrete slabfor abackyard chicken coophelps you learn how to calculate concrete.
Measure the Project Area
How long and wide is the project’s space?
Measure the length of one side, then measure the length of an adjoining side.
Multiply the two figures to arrive at the area.
Example:Thechicken coop’sslab will be 20 feet long and 5 feet wide.
Multiply 20 by 5.
The area is 100 square feet.
Determine the Project Depth
How deep is the concrete fill?
Measure the project’s depth.
Example:Thechicken coop’sslab will be 6 inches thick.
Six inches is the same as 0.5-foot.
So, the depth of the slab will be 0.5-foot.
Calculate the Project Volume
Multiply the area by the depth to arrive at volume.
Example:100 square feet of area multiplied by 0.5-foot depth is 50 cubic feet.
But how many bags ofdryconcreteshould you buy?
What Is a Cubic Foot?
But that’s not what you need.
you better find out how much concrete is produced after the concrete has been mixed with water.
To fill 1 cubic foot, you’ll need 133.33 pounds of dryconcrete mix.
Example:The chicken coop form needs to be filled with 50 cubic feet of wet concrete.
Multiply 50 by 133.33 to arrive at 6,666 pounds of dry concrete mix needed.
Check specifications to see if the product’s figures are the same.
If not, adjust accordingly.
Just divide the total weight needed by the weight in each bag.
Example:The coop slab needs 6,666 pounds of dry concrete.
You found a good price on palletized 80-pound bags of fast-mix concrete.
Dividing 6,666 by 80 produces the rounded up number of 84.
So, for the slab, you need 84 bags (or two pallets) of 80-pound concrete.
For large projects, it’s easier and less expensive to buy bags of concrete by the pallet.
Each pallet holds 42 bags of 80-pound concrete.
Water is then added on top of the dry mix.
The number of 50-pound bags of dry concrete you will need for the following configurations is:
