Concrete Block (CMU) Calculator
Enter your wall size to estimate the number of concrete blocks, bags of mortar, and courses needed — with a waste factor built in.
How to Calculate Concrete Blocks
Find the wall area by multiplying length × height in feet. A standard 8" × 16" CMU covers about 0.89 ft² of face area, which works out to roughly 1.125 blocks per square foot once the mortar joints are included. Multiply your wall area by the blocks per square foot, add about 5% for breakage and cuts, and round up to whole blocks.
For mortar, a common rule of thumb is about 3 bags per 100 blocks, though it varies with joint thickness and block type. The number of courses is the wall height in inches divided by 8, since a standard block plus its joint stacks at 8 inches. Use these figures as a planning estimate and confirm against your block manufacturer's specifications.
Frequently Asked Questions
How many concrete blocks do I need?
Multiply your wall length by its height to get the area in square feet, then multiply by the blocks per square foot for your block size (about 1.125 for standard 8 × 16 block) and add a waste factor. Round up to whole blocks.
How many blocks per square foot?
A standard 8-inch by 16-inch concrete block covers about 1.125 blocks per square foot of wall once mortar joints are counted. Half-high 8 × 8 blocks take about 2.25 per square foot because they are half the face size.
How much mortar for a block wall?
Plan on roughly 3 bags of mortar for every 100 blocks. The exact amount depends on joint thickness, block type, and your mix, so buy a little extra and confirm against the mortar manufacturer's coverage.
Turn Your Measurements Into a Real Floor Plan
Once you know your dimensions, generate a labeled, to-scale floor plan in seconds — then export it to DXF or build it in 3D. No CAD experience needed.
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