Concrete Block Calculator
Enter wall dimensions and block size to instantly compute the number of concrete blocks and material cost. Ideal for partitions, planters and small structures.
Input Data
Results
At a glance:The block calculator uses a "wall area ÷ block area with joint" model. The block area with joint includes the block plus surrounding mortar, i.e. (block length + joint) × (block height + joint); required blocks = ceiling of wall area × (1 + wastage%) ÷ block area with joint; total cost = blocks × price per block.
Formula
Wall area A = wall length × wall height
Block area with joint a = (block length + joint) × (block height + joint)
Blocks N = ⌈ A × (1 + wastage%) ÷ a ⌉
Total cost = N × price per block
Example: 10m×2.5m wall, 390×190mm block, 10mm joint, 5% wastage → about 329 blocks
$$A = L \times H$$$$a = (l_b + m)(h_b + m)$$$$N = \left\lceil \frac{A(1+w\%)}{a} \right\rceil$$How to Use
- Enter the wall length and height.
- Enter the block length and height (mm).
- Set the mortar joint width (usually 10 mm).
- Set the wastage percentage (default 5%).
- To estimate cost, enter the price per block.
- The tool outputs wall area and blocks needed.
Approx. blocks per m² for common block sizes (with 10 mm joint, excl. wastage)
| Block size | Area per block (with joint) | Approx. per m² |
|---|---|---|
| 390 × 190 mm | 0.08 m² | ~12.5 blocks |
| 400 × 200 mm | 0.0861 m² | ~11.6 blocks |
| 450 × 225 mm | 0.109 m² | ~9.2 blocks |
Actual quantity depends on openings (doors/windows) and wastage; add 5% when ordering.
Case Studies
Home partition wall
A 4 m × 2.5 m partition between living room and bedroom.
Using 390×190 mm blocks with 10 mm joint, wall area 10 m².
With 5% wastage about 132 blocks needed.
Planter
Rooftop planter edge 8 m long, 0.6 m high.
Wall area 4.8 m², about 63 blocks.
Buy a few extra for cutting breakage.
Small storage
Backyard small storage, four walls total 20 m long, 2.4 m high.
Total wall area 48 m², about 630 blocks.
Multiply by price per block for material cost.
FAQ
How are blocks calculated?
Blocks needed = wall area × (1 + wastage%) ÷ block area with joint, rounded up. The block area with joint already includes the mortar.
Difference between concrete block and red brick?
Concrete blocks are larger and lighter, suited to partition walls; red bricks are smaller and heavier, used for load-bearing walls and wet areas.
How to handle windows and doors?
Subtract the window/door area from the wall area first. If there are few openings, adding 5% wastage usually covers it.
What joint width is normal?
Usually 10 mm. The joint affects the block area with joint; wider joints spread more area per block and slightly reduce the count.
How many blocks per m² of wall?
390×190 mm blocks with 10 mm joint need about 12.5 blocks/m²; 400×200 mm about 11.6 blocks/m².
Related Tools
References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.