Concrete Block Calculator

The Concrete Block Calculator is a practical tool designed for masons, contractors, and DIY enthusiasts planning to build a wall using concrete masonry units (CMUs), commonly known as concrete blocks or cinder blocks. It helps you accurately estimate the number of blocks and the amount of mortar required for your project, which is essential for budgeting and material purchasing.

How to Use the Calculator

To get an accurate estimate, you'll need to provide the following information:

1. Wall Dimensions: Enter the total length and height of the wall you plan to build.
2. Block Size: Select the dimensions of the concrete blocks you will be using. The calculator includes standard sizes, but you can also enter custom dimensions. Note that standard block dimensions like 8x8x16 inches are "nominal" and typically include the width of a standard mortar joint (3/8 inch). The calculator accounts for this.
3. Mortar Joint Thickness: A standard mortar joint is 3/8 inch. You can adjust this if your project requires a different thickness.

Once the information is entered, the calculator will provide the total number of blocks needed and an estimate of the mortar required in both cubic feet and the number of bags.

Understanding the Calculations

1. Calculating the Number of Blocks

The calculator first determines the effective size of one block, including the mortar joint.

Effective Block Length = Block Length + Mortar Joint Thickness

Effective Block Height = Block Height + Mortar Joint Thickness

Next, it calculates how many blocks are needed horizontally and vertically:

• Blocks per Row (Horizontally): Wall Length / Effective Block Length
• Number of Rows (Vertically): Wall Height / Effective Block Height

The total number of blocks is then found by multiplying these two results:

Total Blocks = Blocks per Row × Number of Rows

The calculator automatically rounds up to ensure you have enough blocks.

2. Calculating the Mortar Needed

Estimating mortar is more complex. The calculator determines the volume of all the horizontal (bed) joints and vertical (head) joints.

• Horizontal Joint Volume: Wall Length × Number of Rows × Mortar Joint Thickness
• Vertical Joint Volume: (Blocks per Row - 1) × Number of Rows × Block Height × Mortar Joint Thickness

The sum of these two volumes gives the total mortar volume needed. This volume is then converted into an estimated number of standard bags (e.g., 60lb or 80lb bags), as each bag yields a specific volume of mixed mortar.