CMU Block Calculator
Block count, mortar, sand, and grout for a concrete block wall. Uses standard mason estimating rules.
The estimating rules this uses
| Item | Rule |
|---|---|
| Block | 1.125 block per sq ft of wall (112.5 per 100 sq ft) for 8 x 8 x 16 nominal |
| Mortar | 3 bags per 100 block |
| Sand | 1 ton per 250 block (4 tons per 1,000) |
| Grout, solid | 0.63 yd3 per 100 block at 6 in, 0.93 at 8 in, 1.22 at 10 in, 1.44 at 12 in |
Grout figures assume fully grouted cells. Partial grouting scales down by the fraction of cells filled.
CMU estimating FAQ
How many concrete blocks per square foot?
A standard 8 x 8 x 16 nominal block covers 0.889 square feet of wall face, so you need about 1.125 blocks per square foot, or 112.5 blocks per 100 square feet of wall.
How many bags of mortar per 100 block?
Plan on 3 bags of mortar per 100 block, plus about 1 ton of mortar sand per 250 block if you are mixing on site.
How much grout to fill CMU cells?
Fully grouted, 100 blocks take about 0.93 cubic yards for 8 inch block, 0.63 for 6 inch, 1.22 for 10 inch, and 1.44 for 12 inch. Grouting every 32 inches on center uses roughly a third of that.
How many blocks high is an 8 foot wall?
Twelve courses. Each 8 x 8 x 16 block plus its mortar joint stacks 8 inches, so 8 feet of height is 12 courses.
Do I subtract door and window openings?
Yes for anything over about 10 square feet. Small openings usually wash out in the waste factor because you still cut blocks around them.
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