Concrete Block Calculator
Estimate how many concrete blocks are needed to build a wall of a given size.
Estimate how many concrete blocks are needed to build a wall of a given size.
How Concrete Block Calculator Works
Wall area is divided by the face area of a standard concrete block (commonly 16 inches by 8 inches including the mortar joint), with a waste allowance added for cuts and breakage.
Who Uses Concrete Block Calculator and Why
- Estimating block count for a foundation wall or retaining wall before ordering material.
- Comparing material needs for a standard 16x8 inch block wall against a different block size.
- Working out how waste percentage affects total block count on a wall with corners or openings.
Mistakes to Avoid
- Leaving waste at the 5% default for a wall with lots of corners, openings, or a non-standard layout, when a more complex wall shape may call for a higher allowance similar to brick.
- Assuming block and brick waste percentages should be the same — blocks are larger and involve fewer pieces per square foot, which is why the default here (5%) is lower than the brick calculator's default (10%).
- Using the default 16-inch by 8-inch face dimensions for a project actually using half-blocks, cap blocks, or a different regional block size without adjusting the fields.
Tips for Best Results
- Measure your actual block's face dimensions, including its intended mortar joint, if you're using anything other than a standard 16x8 concrete masonry unit.
- For a wall with door or window openings, subtract that opening area from gross wall area before entering wall length and height.
Fixing Common Problems
My block count seems too low for a wall with a lot of corners. — Increase the waste percentage above the 5% default — while concrete blocks generally need less waste allowance than bricks, a wall with many corners, openings, or courses still needs more cutting than a plain straight run.
Terms Explained
Concrete masonry unit (CMU): The formal term for a standard concrete block, commonly sized around 16 inches by 8 inches on its face.
Face area: The visible front surface area of a single block as laid in a wall, including its standard mortar joint allowance.