Concrete Block Calculator
Enter the wall length and height to get the number of concrete masonry units. Block sizes are nominal, which means the standard 3/8 inch mortar joint is already included.
Result
- Blocks before waste
- 180 blocks
- Net wall area
- 160 sq ft
- Blocks per square foot
- 1.125
Formula
- Wall area = length × height − openings
- Blocks = wall area ÷ block face area
- Standard block face = 16 in × 8 in = 0.889 sq ft, so 1.125 blocks per sq ft
How the Concrete Block Calculator works
A standard concrete block measures 15 5/8 in × 7 5/8 in on its face. With a 3/8 in mortar joint it occupies a nominal 16 in × 8 in, which is the size used for estimating. That gives 1.125 blocks for every square foot of wall.
Subtract doors and windows as openings, then add a few percent for cuts and breakage.
Worked example
A wall 20 ft long and 8 ft high has 160 sq ft of face. At 1.125 blocks per square foot it needs 160 × 1.125 = 180 blocks. With 5 percent waste, order 189.
Frequently asked questions
How many blocks are in a square foot of wall?
For standard 16 × 8 inch nominal blocks, 1.125 blocks cover one square foot, because each block covers 0.889 square feet including the mortar joint.
Is a cinder block the same size as a concrete block?
Yes for estimating. Both are sold in the same nominal sizes. The names differ by the aggregate used, not the dimensions.
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