CalcConcrete Block Calculator
Last updated: 2026-05-09
Use the Concrete Block Calculator to get instant, accurate results. Enter your values below.
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Common Sizes — Click to Fill
| Wall length (m) (m) | Wall height (m) (m) | Deduct openings (m²) (m²) |
|---|---|---|
| 5 m | 2.5 m | 0 m² |
| 8 m | 2.5 m | 0 m² |
| 10 m | 2.7 m | 2 m² |
| 15 m | 3 m | 4 m² |
Popular combinations
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What are Concrete Blocks?
Concrete blocks (CMUs) are large masonry units used for walls, foundations, and retaining structures. Standard 40×20×20cm blocks yield approximately 12.5 units per m². They're faster to lay than bricks and provide good structural strength.
Calculation Method
Net area = (Length × Height) - Openings
Blocks = Net area × 12.5 per m² × 1.05 (waste)
Worked Example
Wall 10m × 3m with 3m² openings:
- Net area = 30 - 3 = 27 m²
- Blocks = 27 × 12.5 × 1.05 = 354 blocks
- Mortar = 27 × 12 kg/m² = 324 kg
Common Mistakes
- Not accounting for waste from cuts at corners and intersections
- Using incorrect block yield for non-standard sizes
- Not ordering special blocks for corners and lintels
Frequently Asked Questions
Standard 40×20×20cm blocks: 12.5 units per m² including 10mm mortar joints. Hollow blocks may have different coverage.
Use type N mortar (1:1:6 cement:lime:sand) for above-grade walls, type S (1:0.5:4.5) for below-grade or retaining walls.