Autoclaved Aerated Concrete (AAC) Block Calculator
About AAC Block Calculation
The calculator estimates the quantity of autoclaved aerated concrete (AAC) blocks for external walls and, if needed, for internal partitions. It also determines the masonry area, the block volume for purchasing, the total joint length, the approximate dry adhesive consumption, the number of U-blocks, reinforcement parameters, as well as the wall weight and approximate wall loads.
This type of calculation is used for the preliminary selection of materials for a house, garage, extension, and other aerated concrete buildings. The calculator is suitable both for a quick purchasing estimate and for comparing several options for block size, wall thickness, wall height, and waste allowance percentage.
Reference Points and Recommendations
Masonry geometry and wall height
Calculation basis - the total wall length in plan, the masonry height, and the opening area. First, the calculator determines the design length of the load-bearing walls according to the selected building layout. The external perimeter uses the wall length in plan, and if the internal load-bearing wall C is included, its length is also added to the load-bearing wall calculation.
Wall height is calculated from the number of rows of standard blocks, the block height, and the adhesive joint thickness. The calculation follows row logic rather than a direct input of total wall area.
H = n × h + (n - 1) × s
Where H is the masonry height, mm, n is the number of block rows, h is the height of one block, mm, and s is the joint thickness, mm. If the top row of U-blocks is enabled, their height and one additional joint are added to the total height.
Partitions are calculated separately when included. They use their own length, optionally their own height, their own block dimensions, partition door openings, and a separate reinforcement calculation.
Wall area, openings, and gables
Masonry area for external walls is determined as the total load-bearing wall length multiplied by the calculated height. For partitions, the calculation is performed separately using their own length and height. All dimensions are converted from mm to m, so the final area is given in m2.
A = L × H
Where A is the masonry area, m2, L is the total wall length, m, and H is the wall height, m.
Openings are deducted from the masonry area only if this option is enabled. The area of each window and door type is calculated separately, then all values are summed. For external walls, windows and doors are deducted, and for partitions, only partition doors are deducted.
Aopen = b × h × n
Where b is the opening width, h is the opening height, and n is the number of identical openings.
Gables are added as triangular masonry sections. Their area is calculated using the triangle formula.
Afront = b × h / 2 × n
Where b is the gable width, h is the gable height, and n is the number of gables. Depending on the selected option, this area is added either to the external walls or to the partitions.
Block quantity and final purchase volume
Block quantity is determined from the net masonry area after deducting openings and adding gables. The visible area of one block in the wall is taken as its length multiplied by the height of its face.
N = ceil(A / Ablock)
Where A is the net masonry area, m2, and Ablock is the face area of one block, m2. The result is always rounded up because blocks are purchased as whole units.
U-blocks are calculated separately. For the top row, their quantity is determined from the total load-bearing wall length divided by the U-block length including the joint. For lintels above windows and doors, the calculator evaluates each opening separately. The width of each opening is increased by a bearing length of 250 mm on each side, which means 500 mm in total, and the result is then divided by the U-block length and rounded up.
NU,open = ceil((b + 500) / lU)
Final quantity of standard blocks is reduced by the number of blocks replaced by U-blocks above openings. After that, the selected waste allowance percentage is applied to standard blocks, U-blocks, reinforcement, and adhesive.
Nfinal = ceil(N × (1 + p / 100))
Where p is the waste allowance, %.
Block volume for purchasing is calculated from the geometric volume of one block in m3, multiplied by the final quantity of blocks for walls and partitions. This result is useful when ordering material by volume on pallets.
Joint length and dry adhesive consumption
Horizontal joints are calculated from the total wall length and the number of rows. For standard masonry, the number of joints between rows is used, which is n - 1. If the top row of U-blocks is enabled, one more horizontal joint is added along the load-bearing wall length.
Lh = L × (n - 1)
Vertical joints are determined from the number of blocks in each wall segment. For each straight wall segment, the calculator divides its length by the module along the block length (block length + joint), obtains the number of blocks in one row, and multiplies the number of vertical joints by the number of rows. Then all segments are summed.
Dry adhesive is calculated approximately from the masonry volume. For both external walls and partitions, the same specific rate of 25 kg/m3 of masonry is used. This value is convenient for preliminary purchasing, although the actual consumption depends on block geometry, surface quality, and the application tool.
G = 25 × V
Where G is the dry adhesive weight, kg, and V is the masonry volume, m3.
Adhesive for horizontal joints only is distributed proportionally according to the share of horizontal joints in the total joint length. This is useful when vertical joints are filled with another material.
Wall and partition reinforcement
Reinforcement spacing is defined as every Nth row. The calculator always includes the first reinforced row, then adds the following rows at the selected spacing. The number of reinforced rows is determined from the total number of masonry rows.
narm = floor((n - 1) / N) + 1
Reinforcement length for walls is obtained as the total load-bearing wall length multiplied by the number of reinforced rows, the number of bars per row, and the waste allowance factor. If opening consideration is enabled, additional reinforcement below windows is included. For each window, its width is increased by 500 mm on each side, which means 1000 mm in total.
Larm,win = b + 1000
Reinforcement weight is calculated from the length, diameter, and steel density of 7850 kg/m3. If mesh is selected, the calculator does not output weight but the strip length and strip area. The mesh area is determined as the strip length multiplied by the wall or partition thickness.
Block weight and approximate loads
Block weight is determined from the volume and the selected aerated concrete density in kg/m3. The density can be entered separately for external walls and partitions. If U-blocks are included, their volume is also added to the volume of the load-bearing walls.
m = V × ρ
Where m is the weight, kg, V is the block volume, m3, and ρ is the density, kg/m3.
Line load for load-bearing walls and partitions is calculated as the self-weight of the corresponding blocks, converted into force using gravitational acceleration 9.81 m/s2, divided by the total length of these walls. The result is shown in kN/m.
q = (m × 9.81 / 1000) / L
Average bearing pressure on the support is calculated approximately as the total vertical load from all blocks divided by the wall bearing area. The bearing area is taken as the sum of the products of the length of each wall group and its thickness. This result is useful only for a preliminary assessment and does not replace a structural foundation design.
European standards references
Geometry and materials in the calculation follow the general European design approach for masonry structures, where masonry dimensions, self-weight, and loads are determined from geometry and material density. For the verification of load-bearing capacity, slenderness, walls, lintels, and details, it is appropriate to refer to EN 1996-1-1 Eurocode 6. Design of masonry structures. Part 1-1 and EN 1996-2 Eurocode 6. Design of masonry structures. Part 2.
Loads and their combinations in the project should be evaluated according to EN 1990 Eurocode. Basis of structural design and EN 1991-1-1 Eurocode 1. Actions on structures. Part 1-1. Densities, self-weight and imposed loads for buildings. The calculator provides a practical preliminary estimate of material quantities and self-weight, but it does not perform a full code-based structural design of the building.
FAQs
Why is the number of blocks not calculated only from the wall volume?
For purchasing, the number of whole blocks is more important than only the total masonry volume. That is why the calculator first determines the net wall area, then divides it by the face area of one block, and rounds the result up to a whole quantity.
Why are U-blocks calculated separately?
U-blocks are often used in the top row and above openings to form lintels and reinforced concrete bond beams. They take the place of standard blocks, so the calculator evaluates them separately and reduces the quantity of regular blocks above openings.
Why is the adhesive consumption given as an approximate value?
Dry adhesive consumption depends on block dimensional accuracy, joint thickness, the application method, and workmanship quality. The calculator uses one reference value of 25 kg/m3 of masonry, which is usually sufficient for a preliminary purchase estimate.
How is reinforcement below windows calculated?
If opening consideration is enabled, the calculator adds a separate reinforcement length below windows. For each window, it uses the window width plus 500 mm of extension on each side to provide a more realistic estimate of reinforcement bars or mesh.
Can the load result be used to choose a foundation?
For a preliminary assessment, yes, because the calculator shows block weight, line load in kN/m, and average bearing pressure on the support. For final foundation selection, a separate design is required, taking into account floors, roof, snow, imposed loads, ground conditions, and Eurocode requirements.