Calculate how many concrete masonry units (CMU blocks) and mortar bags you need for a wall, based on wall size and standard block dimensions.
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This calculator divides the total wall area (plus a waste allowance) by the block's nominal face area: Blocks Needed = (Wall Area × (1 + Waste%)) ÷ (Block Length × Block Height ÷ 144), using nominal dimensions (which already build in a standard mortar joint, unlike raw brick dimensions). This is a completely different calculation from our Concrete Calculator, which estimates poured, mixed concrete by volume for slabs and footings, not discrete block units for a wall.
The default 16 in × 8 in nominal size reflects the most common standard concrete block used in the US, though the actual block (before accounting for the mortar joint) measures closer to 15.625 in × 7.625 in. Always confirm the exact block size you're using, since other sizes (like 4 in or 12 in wide blocks) are also common depending on the application.
Both count discrete masonry units for a wall, but concrete blocks (CMU) are much larger than standard bricks and use nominal sizing that already accounts for the mortar joint, while the Brick Calculator asks for the brick's raw size and joint thickness separately.
Nominal dimensions describe a block's size including its allowance for a standard mortar joint, which is why a 'nominal 16x8' block is actually manufactured slightly smaller (commonly 15.625 in × 7.625 in), so that once mortared in place, it occupies the full nominal footprint.
No, this calculates blocks for the total wall area you enter. Subtract the area of any door or window openings from your wall area before entering it for a more accurate count.
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