Concrete Block Fill Calculator

Finding the core fill volume of a concrete block (also known as a CMU, or Concrete Masonry Unit) involves calculating the space inside the hollow core of the block that will be filled with material (usually grout or concrete). The core fill volume is important for ensuring the correct amount of material is used for reinforcement, particularly in walls and structures that require extra strength or stability.

To calculate the volume of each block void in a concrete masonry unit (CMU), you need to start by determining the total size of the block and then accounting for the shells and webs that make up the block’s structure. Here's a step-by-step breakdown:

1. Measure the Block's Dimensions:
   • The standard size for a CMU is 8" x 8" x 16", but variations do exist.
   • In this case, assume the block measures 8" high, 8" wide, and 16" long.
2. Consider the Block’s Shells and Webs:
   • Each CMU consists of two shells (front and back) and typically two or three webs (running from the front to the back of the block).
   • The shells are the thicker parts of the block, while the webs divide the block into hollow spaces (cells).
3. Account for the Thickness of Shells and Webs:
   • Measure the thickness of the shells and webs. For example, let’s say the shell thickness is 1" on each side, and the web thickness is 1".
   • Subtract the thickness of the shells from the width of the block and the thickness of the webs from the length to find the internal dimensions of the void.

Width: 8″ – 1″ (shell) – 1″ (shell) = 6″
Length: 16″ – 1″ (web) – 1″ (web) – 1″ (web) ÷ 2 cells = 6.5″
Height: 8″

Multiply the new width and length by the height of each block to get the cubic inches for that block:

6″ × 6.5″ × 8″ = 312 cu in/block