Concrete block calculator for walls
Works with common block sizes such as 400 × 200 mm and with any face size you enter.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter wall length, wall height, doors and windows area, block length, block height and mortar joint.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Blocks per m² = 1,000,000 ÷ ((block length + joint) × (block height + joint)) in mm. Count = (length × height − openings) × blocks per m² × (1 + waste ÷ 100), rounded up.
Example
Inputs: Wall length = 10 m, Wall height = 3 m, Doors and windows area = 0 m², Block length = 390 mm, Block height = 190 mm. Result: Blocks to buy (with waste): 394 pcs; Net blocks: 375 pcs; Blocks per m²: 12.5.
Limits and caveats
- Counts a single-leaf wall and ignores concrete columns and lintels inside it.
- Mortar is not estimated because hollow blocks take far less than solid ones.
Questions about this tool
How many blocks per square metre?
A 390 × 190 mm block with a 10 mm joint takes 400 × 200 mm, so 12.5 blocks fit in 1 m².
What if my block is a full 400 × 200 mm?
With a 10 mm joint the cell becomes 410 × 210 mm, about 11.6 blocks per m².
Does block thickness change the count?
No, the count per m² depends only on the block face, though thickness changes weight and mortar.