The Ultimate Concrete Calculator (Cubic Meters/Yards & Bags)

This calculator can help you determine how many cubic meters, cubic yards, or bags of concrete your project requires. In fact, it is capable of performing calculations for various applications including slabs, footings, walls, rectangular columns, rectangular holes, circular columns, circular holes, curb and gutter barriers, solid stairs, and stairs.

The importance of determining the right volume or number of bags

Basically, it is very important to know how much concrete you need for a specific project. For instance, with improper calculations, you can end up ordering less than the required volume, or even much more than required. In fact, in both cases, this is considered as a bad practice. Specifically, ordering less than the required volume requires an additional short load, which costs more per unit volume. In addition, this can cause delays, which increases labor costs, or even increases the chances of cold joints! On the other hand, ordering much more than the required volume is an undesired increase in costs and wastes in concrete.

Hence, one should perform calculations and know how much concrete is needed, with an additional safety margin to the volume. Thereby, we recommend ordering a little bit more than the calculated volume, for example 5 or 10%, depending on the dimensions, waste, sloping, finishing, etc… .  

This calculator is quite straight forward and simple to use. It mainly consists of a top horizontal tab, where the user can select the application, including:

1. Slabs and Footings.
2. Walls.
3. Rectangular Columns and Holes.
4. Circular Columns and Holes.
5. Curb and Gutter Barriers.
6. Solid Stairs.
7. Stairs.

In addition, each tab consists of three sections, the input of dimensions, entry of data related to concrete bags, and the results section. It is important to note that the main purpose of the second section (entry of data related to concrete bags) is to make this concrete calculator highly accurate when calculating the number of bags. In addition, this section improves the flexibility of this calculator, allowing the user to enter some advanced data when working with concrete bags.

Step #1: Select the application

First, the user has to select the tab which matches their application. For instance, if the user wants to figure out how many cubic meters, cubic yards, or number of bags are required for a slab on ground application, they should select the “Slabs & Footings” tab.

Step #2: Enter the dimensions

Second, the user should enter the dimensions in the first section of this concrete calculator. This section consists of several fields related to the dimensions, in addition to an explanatory illustration. Besides, it is important to make sure that the values match the unit right next to each field, for example meters, centimeters, feet, inches, etc….

Step #3: Enter the data related to bags (optional)

Third, the user can provide some essential data related to concrete bags. In fact, this section is mostly optional, since this concrete calculator has pre-defined approximation values in some fields, except for the size of bags. However, entering the exact values for the product in use increases the accuracy of the results. Here, the user can specify the size of the concrete bag in kilograms (metric) or pounds (imperial), the density of concrete in kg per cubic meter or pounds per cubic foot, and the required water for each bag in liters or quarts. Basically, this data is easy to obtain, and is often available on the bags or from the supplier.

Step #4: Check your results

Fourth, the calculator presents the results in two fields. The first field is the volume in cubic meters or cubic yards, and the second field is the number of pre-mixed concrete bags. Besides, it is important to note that the latter field rounds up to the nearest integer. For example, if the number of bags is 1.4, it rounds the value up to show 2 bags. Hence, it is important to take into account this note especially when adding values for multi small applications.

Example

How many cubic meters of ready mix concrete should we order for an 8m x 14m slab on ground with 15cm thickness?

Solution

Based on the given data, we will follow the steps as follows:

1. Select “Slabs & Footings” tab.
2. In the first section, we will enter the dimensions as 8, 14, and 15 for the length (m), width (m), and thickness (cm), respectively.
3. Since we are working with ready mix concrete and not bags, we will not input any additional data in the second section.

Hence, the calculator presents the volume of concrete as 13.440 cubic meters.

However, this value represents the exact volume without taking into account any wastage, substrate and surface flatness, and other factors. Thereby, in this example, we will consider ordering 14 cubic meters, which accounts for about 4.16% additional concrete than the calculated value.

Example

Determine how many cubic yards of concrete or 80-lb bags are required for the following solid stairs project:

• Rise = 6″.
• Run = 12″.
• Platform = 30″.
• Width = 40″.
• Number of risers = 4.

Solution

Based on the given data, we will first select the “solid stairs” tab. Next, we will fill in the dimensions in the first section. Then, in the data entry of concrete bags section, we will specify 80 pound bags, and leave the rest of the fields for the predefined values.

In brief, the results show that this project requires almost 1 yard of concrete or 45 80-lb bags of pre-mixed concrete.

Example

A 72 feet long wall is to be constructed on an existing concrete footing. This wall has a height of 8 feet and a thickness of 8 inches. How many cubic yards of concrete should you order?

Solution

First, we will select the “walls” tab. Second, we will enter the given dimensions in the three fields in the first section. However, in this example, we are performing calculations to order ready mix concrete, and not pre-mixed bags. Hence, we will leave the second section, which is related to concrete bags, as it is.

Thereby, the results show that this wall requires almost 14.222 yards of concrete.

However, taking into account wastage, slight measurement defects, and other factors, we will consider ordering 15 cubic yards for this wall.