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When it comes to your next masonry project, concrete and cement can get pretty expensive. Also, due to the calculations involved, ordering concrete might be the toughest job for many people.

However, with proper planning and calculations, you can easily estimate how much concrete would suffice for your project and avoid overspending. Similarly, you also don’t want to order less material and then re-order as that’ll increase cost in transportation.

To help you simplify things, we are here with various formulas that can give an estimate of how much concrete your project requires based on the shape of the area.

Before we begin this DIY project, make sure you have a tape measure and a calculator in place.

Concrete Calculator Formula for Different Shapes

As it goes without saying, the very first thing you need to know is the shape of the area. Based on the shape, the measurements will vary.

Note: We’ll use the default measurement unit as feet and write formulas accordingly. However, since all concrete is estimated in cubic yards where one cubic yard = 27 cubic feet.

To calculate volume in cubic yards, you’ll need to divide volume in cubic feet by 27:

Volume in Cubic Yards (yd3) = Volume in Cubic Feet (ft3) ÷ 27

1. Rectangle

Calculating the volume of a rectangle or square area is very easy. You just need to multiply the length by width by thickness.

Volume in Cubic Feet (ft3) = Width x Length x Thickness

2. Triangle

In the case of a triangular structure, you need to measure the base and height. The volume can be found by multiplying the base length times the height length and divide by 2.

Volume in Cubic Feet (ft3) = Base x Height x ½

3. Circle

Circular or round slab areas can be difficult to calculate. We’ll first need to calculate the area using its radius and then multiply by Pi (Pi = 3.14)

Area in Cubic Feet (ft3) = Radius² x 3.14

To calculate volume, we’ll multiply the total area by the depth of the slab.

Volume in Cubic Feet (ft3) = Depth x Area

4. Hexagon

It may sound complicated, but it’s pretty easy to calculate the total concrete estimation for a hexagon structure. Similar to circle, we’ll first need to calculate the area of the surface using below formula:

Area in Cubic Feet (ft3) = (Length of The Side² x 5.19) ÷ 2

To get the volume, we’ll multiply the total area by the height of the hexagon.

Volume in Cubic Feet (ft3) = Area x Height

5. Irregular Shape

An irregular shape structure would be more common in real life and it can be tricky to calculate the total volume in this case. To simplify, you’ll first need to draw the project out on graph paper with ¼ inch representing 1 foot (or smaller if the project is of bigger size)

Once you have drawn the total project, try to identify all the rectangles available and number them. Now, use the formula we shared for the rectangle to calculate the volume for each of the rectangle available.

For example, if there are 3 rectangles, you’ll calculate volume like this:

Rectangle 1 Volume in Cubic Feet (ft3) = Width x Length x Thickness

Rectangle 2 Volume in Cubic Feet (ft3) = Width x Length x Thickness

Rectangle 3 Volume in Cubic Feet (ft3) = Width x Length x Thickness

After you’ve calculated individual volume, we need to add them to get the total volume of the surface.

Total Volume in Cubic Feet (ft3) = Rectangle 1 + Rectangle 2 + Rectangle 3

The above formulas will give you a good estimate of how much raw materials of concrete you need for the project. However, to be on the safer side, we recommend adding 10% to the final number that will cover spillage and slab depth variations. It’ll give you a much better cost per yard estimation.

Once you’ve figured out exactly how much concrete you need, there are two ways to order concrete – concrete by the yard or concrete bags.

For larger jobs such as concrete driveways, ordering concrete by the yard from a ready mix company can be a better choice. However, for smaller jobs, calculating the number of concrete bags would be better.

To give you a quick estimate, this is how much yields you can expect based on concrete bag size:

  • 40-pound bag = 0.011 cubic yards
  • 60-pound bag = 0.017 cubic yards
  • 80-pound bag = 0.022 cubic yards

Final Words

Concrete work is challenging and can be very expensive to do on your own. However, if you are confident enough, you must take the time to do the calculations and create an estimate. With the formulas shared above, you can quickly prepare the estimation and order the right amount of concrete.

While it’s not as complicated, some people may simply dread calculation and worry about miscalculations. If that’s the case, you should leave the entire calculation to your concrete contractor company.

Feel free to reach out to us and discuss your concrete work. We are one of the top concrete contractor companies in Miami with over 10 years of experience.