Concrete Block Calculator
Estimate concrete blocks and mortar for a wall, minus openings.
Blocks needed
142 blocks
- Net wall area
- 120 sq ft
- Mortar (est.)
- 5 bags
How we calculate this
Net wall area (gross area minus openings) is divided by the face area of a single block (typically 8" × 16" = 0.89 sq ft) to get blocks needed, then adjusted for waste. Mortar is estimated at roughly 3 bags per 100 blocks.
Example
Measuring tips
Measure wall length and height at the finished dimensions. Measure each door and window opening separately and add them above — they're subtracted from the total area.
Common mistakes
- Forgetting to subtract door and window openings from the wall area.
- Using the wrong block size preset for half-blocks at corners and ends.
- Underestimating mortar — coverage varies with joint thickness and block porosity.
Frequently asked questions
How many blocks are in a standard wall?
Roughly 1.125 blocks per square foot for standard 8x8x16 CMU block — this calculator does that math for your exact wall size.
How much mortar do I need per 100 blocks?
About 3 bags of mortar mix per 100 blocks is a common estimate, adjustable for your joint thickness.
Related calculators
Estimates are provided for planning purposes. Actual material requirements may vary based on supplier specifications, compaction, site conditions, installation method, waste, and local code.