Block Fill Calculator
Estimate grout to fill CMU block cores.
Block-fill grout volume depends on core size: a fully filled 8-inch CMU holds about 0.5 cu ft of grout per block, while a 12-inch block holds about 0.9 cu ft. Multiply the number of filled cells by that volume, divide by 27 to convert it to cubic yards, and add 5–10% for waste. Enter your wall dimensions to estimate cubic yards and bag counts.
Cubic yards
0.322
8.7 ft³
80 lb bags
15
grout mix
Blocks filled
100
at 100%
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Recommended tools & materials
Handy picks for this project on Amazon.
Brick Trowel
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Type S Mortar Mix
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Mason's Line & Line Blocks
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4 ft Masonry Level
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How does the block fill calculator work?
A standard 8×8×16 CMU has ~0.087 ft³ of core volume (both cells). Multiply block count by core volume by the percentage of cells you're filling to get total grout volume.
Which guide explains this in more depth?
- How inspectors check brick and mortar counts on a single-wythe wall. Read the inspector-approved brick calculator method guide for the full worked example.
What else do people ask about this calculator?
How much grout for a CMU wall?
Fully grouted 8 in CMU takes about 1 yd³ per ~310 blocks. Partially grouted (every other cell) roughly halves that.
What mix is used for block fill?
Fine-aggregate grout with 8–11 in slump, ~2000–3000 psi. Sold pre-bagged as 'core fill grout' or 'block fill'.
Which related calculators should I use next?
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Complete Your CMU Grouting Setup
These practical tools help you measure, mix, and place grout accurately when filling CMU cores.
Kraft Tool Grout Bag
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Bon Tool Measuring Bucket
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QEP Professional Mortar Mixer
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