Cubic yards:
80lb Bags:
Estimated cost:
Concrete blocks used for construction, also known as concrete masonry units (CMUs) or cinder blocks, typically have one or two holes or voids known as cells to reduce the weight of the block. These cells are filled with concrete or grout during the installation process to strengthen and reinforce the wall. To estimate how much concrete or grout is needed to fill those cells, you need to find the volume necessary to fill each block, then multiply that by the total number of blocks in the wall.
To get the volume of each block, begin by getting its total size in inches. The standard size for a CMU is 8″ x 8″ x 16″, but there are many variations.
Each CMU is made up of two “shells” along the front and back and two to three “webs”, which run from the front to the back of the block. Measure the thickness of each one, then subtract the width of the shells from the width and the width of the webs from the length of each block.
You will also need the number of cells, with two being standard. You will divide the total length by the number of cells. In a block that measures 8″ x 8″ x 16″, this will look like:
Multiply the new width and length by the height of each block to get the cubic inches for that block:
Keep in mind that CMU measurements are nominal, meaning that they are often slightly smaller than their given measurements to account for the mortar between them. You may also have a block with custom web and shell measurements, which can change the total volume.
To get the most accurate volumes, always measure each area on the block yourself, and use those measurements when doing the calculation. Use our volume calculator to simplify this process.
The next step is to find the number of blocks in the wall. This can be done by counting the number of blocks in the wall, or by getting the square footage of the wall and of the block you want to use and dividing the total square footage of the wall by the square footage of the block.
For an 8 x 16 block, this is 0.89 sq ft. Or, use our concrete block calculator to find how many blocks are in your wall.
Multiply the cubic inches of volume for one block by the total number of blocks in the wall to get the total volume in cubic inches. Divide the final number by 46,656 to find the volume in cubic yards. A conversion calculator can make this easy.