Blocks Needed
350 blocks
Wall Area
320 sq ft
Net Area
296 sq ft
Cost
$875
350
$875
320 sq ft
296 sq ft
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Inputs
Result
Wall area = 40 × 8 = 320 sq ft. Openings = 2 × 3 × 4 = 24 sq ft. Net = 296 sq ft. Blocks = 296 / 0.89 = 333, with 5% waste = 349. Cost = 349 × $2.50 = $828.
Inputs
Result
Wall area = 20 × 4 = 80 sq ft. No openings. Blocks = 80 / 0.89 = 90, with 5% waste = 95. Cost = 95 × $3.50 = $333.
A standard 8×8×16 CMU block covers 0.89 sq ft including mortar joints (8" height + 3/8" joint = 8.375", 16" length + 3/8" = 16.375"). So you need about 1.125 blocks per sq ft.
| Block Size | Face Area (with joints) | Blocks per sq ft | Avg Cost per Block |
|---|---|---|---|
| 4×8×16 | 0.89 sq ft | 1.125 | $1.50–$2.00 |
| 6×8×16 | 0.89 sq ft | 1.125 | $2.00–$2.75 |
| 8×8×16 | 0.89 sq ft | 1.125 | $2.50–$3.50 |
| 12×8×16 | 0.89 sq ft | 1.125 | $3.50–$5.00 |
Subtract the opening area from the total wall area before calculating blocks. For a 3 ft wide by 4 ft tall window, subtract 12 sq ft. This calculator handles multiple openings automatically.
Use 5% for simple straight walls, 7-10% for walls with corners and openings, and 10-15% for complex layouts. Breakage during delivery and cutting around openings accounts for most waste.
| Wall Complexity | Waste Factor | Common Sources of Waste |
|---|---|---|
| Simple straight wall | 5% | Minor breakage during delivery |
| Wall with 1–2 corners | 7–8% | Corner cuts, minor breakage |
| Wall with openings | 8–10% | Cuts around doors/windows |
| Complex layout | 10–15% | Multiple cuts, angles, curves |
Material cost alone is about $2.80-$4.00 per sq ft for blocks ($2.50-$3.50 per block at 1.125 blocks/sq ft). With mortar and labor, installed cost ranges from $10-$17 per sq ft.
| Cost Component | Per sq ft | Per 100 sq ft Wall |
|---|---|---|
| Blocks only | $2.80–$4.00 | $280–$400 |
| Mortar | $0.50–$1.00 | $50–$100 |
| Rebar / fill | $0.75–$1.50 | $75–$150 |
| Labor (mason) | $6.00–$10.00 | $600–$1,000 |
| Total installed | $10–$17 | $1,000–$1,700 |
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Last Updated: Mar 26, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.
