Hollow Block Calculator
Fast, accurate, and free online Hollow Block Calculator tool that runs directly in your browser.
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Hollow block calculator
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Other tools you may find usefulConsumption of wall blocks under control - why are precise calculations important?
The construction of structural and partition walls is one of the most important stages of constructing a shell building. Correctly estimating the number of hollow bricks, concrete blocks or aerated concrete elements is crucial from the point of view of the investment budget. Purchasing too little material generates additional transport costs and downtime for the construction team. In turn, excess ceramic hollow bricks or silicate blocks, after construction, become troublesome waste that is difficult to dispose of or resell without financial loss. Our professional online block calculator allows you to calculate the demand for wall materials (in pieces and pallets) in a fraction of a second based on the dimensions of the partition, the selected type of block and the type of joint.
How to calculate the number of hollow bricks per m² of wall? Mathematical formula
The principle of calculating the number of wall elements is based on determining the wall surface and the front surface of a single block, taking into account the thickness of the joint (mortar). The basic formula is as follows:
Number of blocks (pcs) = Net wall area (m²) / [ (block length + joint thickness) · (block height + joint thickness) ]
Where all dimensions of the block and joint should be given in meters (e.g. joint thickness 12 mm = 0.012 m). The net wall area is determined by adding up the areas of all walls and **subtracting the area of window and door openings**.
For example, if we are building a wall from the popular Porotherm 25 ceramic block (dimensions: length 373 mm, height 238 mm) with a joint of 12 mm thick:
Area of the element with the joint = (0.373 + 0.012) · (0.238 + 0.012) = 0.385 · 0.250 = 0.09625 m².
Consumption per 1 m² = 1 / 0.09625 = 10.4 pieces of hollow brick.
Popular dimensions and performance of wall blocks in Poland
The table below presents a summary of the most popular wall materials used in single-family housing in Poland, along with their dimensions and average performance per square meter of wall:
| Name of the wall material | Standard dimensions (length x width x height in mm) | Type of joint (mortar) | Average consumption per 1 m² | Recommended stock (waste allowance) |
|---|---|---|---|---|
| Porotherm 25 Dryfix(ceramic block) | 373 x 250 x 249 mm | Foam glue (thin layer) | 10.7 pcs./m² | Approx. 5% |
| Porotherm 25 P+W(traditional) | 373 x 250 x 238 mm | Traditional mortar (12 mm) | 10.7 pcs/m² | Approx. 5% |
| Ytong Forte 24(aerated concrete) | 599 x 240 x 199 mm | Thin-layer adhesive (2 mm) | 8.3 pcs/m² | Approx. 8% |
| Solbet Optimal 24(aerated concrete) | 590 x 240 x 240 mm | Thin-layer adhesive (2 mm) | 7.0 pcs/m² | Approx. 8% |
| Silka E24 silicate block | 333 x 240 x 199 mm | Thin-layer adhesive (2 mm) | 15.0 pcs/m² | Approx. 7% |
| Classic solid brick(for walls) | 250 x 120 x 65 mm | Traditional mortar (12 mm) | Approx. 51 pcs/m² (thickness 12 cm) | Approx. 10% |
Frequently asked questions (FAQ)
How to calculate how many hollow bricks are needed for a house with an area of e.g. 100 m²?
To calculate this, we do not use the usable area of the house directly (e.g. 100 m²), but we need to determine the **total area of external and load-bearing walls**. We measure the perimeter of the house and multiply it by the storey height (e.g. 2.7 m) to obtain the gross wall area. Then we subtract the area of all windows and doors from this. We multiply the obtained result in m² by the consumption of the selected block per m² (e.g. for Porotherm 25 it is 10.7 pcs.). Finally, we add approximately 5-8% of the stock.
What reserve (allowance) for waste and trimmings should be added?
An allowance for waste should be added to the final calculation result. For straight walls without slopes, it is usually 5% for ceramic blocks and approx. 8% for aerated concrete (which cracks easily during transport and cutting). In the case of a complex house with bay windows, dormers or sloping gable walls, this allowance should be increased to 10-12%.
What is the difference between the consumption of hollow blocks with traditional mortar and with thin-layer adhesive?
With traditional mortar (joint thickness approx. 10-15 mm), the height of the joint has a real impact on saving wall material - minimally fewer blocks are needed per m². In the case of thin-layer/adhesive mortar (joint thickness approx. 1-2 mm, e.g. Ytong or Porotherm Dryfix), the joint can be almost completely omitted in the calculations, and the entire height of the wall is based solely on the physical dimensions of the block.
How many Porotherm 25 blocks are on one pallet?
A standard factory pallet of Porotherm 25 P+W blocks usually holds 60 or 72 pieces (depending on the factory and packaging method). In turn, lighter aerated concrete (e.g. Solbet 24) is packed in 48 pieces per pallet.
What is cheaper to build – aerated concrete (Solbet/Ytong) or ceramics (Porotherm)?
Aerated concrete (blocks) are characterized by larger dimensions, which means that the consumption of pieces per m² is lower (approx. 7-8 pieces vs. 10.7 pieces for ceramics). This translates into faster bricklaying and less adhesive mortar consumption, which can reduce labor costs. However, ceramics is a harder material, with better heat accumulation and higher mechanical resistance.