Concrete Block Calculator
Count the concrete blocks, also called CMU, needed for a wall. Subtract the doors and windows, add a little for breakage, and the number of blocks is ready.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Wall area is length times height, minus the openings. A standard 8 by 16 inch block with its mortar joint covers about 0.89 square feet of wall, so the area is divided by that and rounded up.
Breakage and cutting at the ends use up some extra blocks. Five percent is a common allowance, and a wall with many corners or cuts may need more.
Worked example
A wall 20 ft long and 8 ft high, with 24 ft² of openings, has 136 ft² of block face. That needs 161 blocks with the allowance for breakage added.
Questions
Are these blocks the real size?
They are nominal sizes. An 8 by 16 inch block is measured with its mortar joint, so the block itself is a little smaller.
Does this count the bond beam?
No. A bond beam or special top course is often a different block, so count those on their own.
What about other block heights?
Blocks of a different thickness but the same 8 by 16 face cover the same area, so the count stays the same. For other face sizes, ask the supplier for coverage per block.
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