Concrete Block Calculator
Count the concrete blocks (CMUs) for a wall, with waste.
Estimate the number of concrete blocks (CMUs) for a wall. The standard 16×8 in block (with mortar) covers about 0.89 ft².
How the Math Works
The Concrete Block Calculator uses a straightforward mathematical formula to determine how many concrete masonry units (CMUs) are needed for a wall. The calculation is based on the relationship: blocks per square foot equals 144 divided by the product of block length and block height (144 ÷ (blockL × blockH)). This works because 144 represents the number of square inches in one square foot, and dividing by the block's area in square inches gives how many blocks fit in one square foot. The result is then multiplied by the total wall area in square feet, with an additional waste factor typically added to account for cutting and breakage.
Practical Applications
To use this calculator practically, first measure your wall's total length and height to determine the square footage. Then identify your specific block dimensions - standard concrete blocks are typically 8 inches high by 8 inches long, though other sizes exist. Input these measurements into the formula to calculate blocks per square foot, then multiply by your wall area. Always add 5-10% extra material to your final count to account for waste, broken units, and cuts needed for openings like doors and windows. This ensures you purchase enough blocks without running short during construction.
Day-to-Day Use
This calculator saves homeowners and contractors significant time and money in everyday construction projects. Instead of manually counting blocks or over-ordering materials, you get an accurate estimate that prevents both shortages and costly excess inventory. Whether you're building a backyard retaining wall, constructing a garage foundation, or repairing a section of existing wall, knowing exactly how many blocks you need helps you budget correctly and avoid multiple trips to the supply yard. It's especially valuable for DIY enthusiasts tackling weekend projects who want to get materials right the first time.
Worked example
20×8 ft wall (160 ft²) with 16×8 in blocks → 1.125/ft² → 180 blocks (+5% = 189).
FAQ
How many blocks per square foot?
About 1.125 standard 16×8 in blocks per square foot of wall.