Concrete Block Calculator
Concrete & Masonry · Updated July 2026
Enter your wall area to find how many standard 8×8×16 concrete blocks (CMUs) you need — with a waste allowance built in.
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Estimates only. Add extra for waste and confirm with your supplier.
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How many concrete blocks per square foot?
A standard 8×8×16 block covers about 0.89 sq ft of wall face, so you need about 1.125 blocks per square foot.
Counting concrete blocks
A standard 8×8×16 block covers about 0.89 sq ft of wall face, so you need roughly 1.125 blocks per square foot. Measure the wall area, subtract openings, and add about 5% for breakage.
Mortar and rebar
Plan on about 3 bags of mortar per 100 blocks. For retaining or load-bearing walls, add vertical rebar and fill those cores with grout — check your local code for spacing requirements.
How to use this calculator
- 1Measure the wall area in square feet.
- 2Set a waste allowance.
- 3Read the total block count.
Frequently asked questions
How many blocks do I need?
Multiply wall area by 1.125, then add about 5% for waste and breakage.
How many blocks do I need per square foot?
About 1.125 standard 8×8×16 blocks per square foot of wall.
How many bags of mortar per 100 blocks?
Roughly 3 bags of mortar mix per 100 concrete blocks.
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