Concrete Block Calculator

The key to a strong block wall is Structural Reinforcement. Concrete blocks are strong in compression (weight from above) but weak in "lateral" pressure (pushing from the side, like soil against a retaining wall). To fix this, professionals place Steel Rebar vertically through the hollow cores of the blocks and horizontally in "bond beams." These cores are then filled with Grout (a thin, pourable concrete). Our calculator helps you estimate the number of blocks, but you must consult a structural engineer for the specific rebar spacing and core-fill requirements for your project. A "hollow" block wall is rarely sufficient for anything other than a simple partition.

Another vital consideration is the Footing. A block wall is incredibly heavy; a single 8-inch block weighs about 35-40 pounds. Without a proper "Concrete Footing" (a buried concrete base that is twice as wide as the wall), the wall will quickly sink or tilt. In colder climates, this footing must be below the "frost line" to prevent the ground from heaving the wall upward. Our calculator provides the material for the wall itself, but we recommend using our "Concrete Calculator" to estimate the footing separately. Finally, remember the Waterproofing. If your block wall is for a basement or a retaining wall, you must apply a "bituminous coating" or a waterproof membrane to the exterior. Blocks are porous and will act like a sponge, pulling moisture into your home if they aren't properly sealed from the earth. Our tool gives you the block count, but these secondary layers are what make the wall functional for the long term.