There’s no denying we build with a lot of concrete here in the Caribbean, from our walls to our foundations to our driveways, concrete is an essential component. As many of you may know, calculating the amount of concrete that you need is actually just a little bit of mathematics. This is the same for rectangular footings (a step), cylindrical piers (column), walls and slabs.
- For a round column – multiply the square of its radius (in inches) by pi (3.14) and then multiply the result by the height (in inches) and divide the results by 1,728 to get the cubic feet of concrete required = (radius2 X 3.14) x height)/1728.
- For a rectangular footing – multiply width by length and depth (all in feet or a fraction thereof) = width x length x depth.
- To calculate volumes of irregular shapes, break them down into rectangles, triangles and circles; calculate each separately and then add them together to get your required volume.
Of course you can use a Concrete Calculator to help you along with the calculation.
Now you should add about 5% to your calculation to ensure that you do not run out of concrete, as not having enough concrete can ruin the project.
Important to note that these calculations can be used where premixed concrete is being used and to also validate what your contractor estimates and bills you for on big jobs.
There are other articles that assist with proportions and calculating volumes when mixing your own concrete.