Foam Concrete Block Quantity Calculator
About Foam Concrete Block Calculation
The calculator determines the quantity of foam concrete blocks for exterior walls and, if needed, for interior partitions. It also calculates the total masonry area, the purchase volume of blocks, the total joint length, the estimated dry adhesive consumption, the quantity of U-blocks, the length and weight of reinforcement, as well as the estimated weight and loads from the masonry.
This calculation is suitable for a preliminary estimate of materials for a house, garage, utility building, and other structures made of blocks. The logic is built so that the user sees not only the final quantity in pieces, but also the intermediate meaning of the calculation: which masonry area is taken, what is deducted, how gables, openings, the top U-block course, and the waste allowance are considered.
Guidelines and recommendations
Wall and partition geometry
Wall layout. First, the calculator determines the total length of the exterior load-bearing walls according to the selected house layout. For a rectangular outline, the perimeter is used, while for more complex shapes, intersecting sections are excluded from the total length and interior load-bearing or non-load-bearing walls are added according to the selected configuration.
Masonry area. After that, the wall area is calculated with the formula A = L × H, where A is the masonry area in m2, L is the total wall length in m, and H is the calculated wall height in m. For partitions, the area is calculated separately using the same logic.
Gables. If gable calculation is enabled, their area is added as the area of a triangle using the formula Af = B × H / 2, where B is the gable width in mm and H is its height in mm. This area is then added either to the exterior walls or to the partitions, depending on the selected block type.
Wall height by courses
Wall height. The calculator does not take the exterior wall height as an independent main value, but calculates it from the number of block courses. The formula is H = N × h + (N - 1) × s, where N is the number of courses, h is the height of one block in mm, and s is the thickness of the horizontal joint in mm.
U-blocks. If the top U-block course is enabled, its height and one additional joint are added to the resulting height. In other words, the final height increases by hU + s, where hU is the U-block height in mm.
Partitions. For partitions, the calculator can use either the same height as for the exterior walls or a separate height. In that case, the number of partition courses is found by reverse calculation, that is, by dividing the specified height by the course module h + s and rounding up.
Block quantity
Area of one block. To calculate the quantity of blocks, the calculator uses the face area of the block in the wall, not its volume. For exterior walls, it is determined as Ab = l × h, where l is the block length in m and h is the block height in m.
Blocks for walls. The number of blocks is determined by the formula N = ceil(A / Ab). This means that the total masonry area is divided by the area of one block, and the result is always rounded up to a whole block.
Openings. If deduction of windows and doors is enabled, the calculator first finds their total area. The same principle is used for both windows and doors: A = b × h × n, where b is width, h is height, and n is quantity. The sum of these areas is deducted from the exterior masonry area, while for partitions only door openings may be deducted separately.
Selection of the final value. Exterior walls and partitions are calculated separately, and then a waste allowance in percent is applied to each result. The final quantity of blocks to purchase is the sum of the exterior wall blocks and partition blocks after rounding and adding the allowance.
Block volume and weight
Volume of one block. For purchasing and logistics, the calculator also determines the geometric volume of one block using the formula Vb = l × t × h, where t is the block thickness in m. The total volume of blocks to purchase equals the number of blocks multiplied by the volume of one block.
Masonry weight. If weight calculation is enabled, the mass of exterior and interior blocks is determined separately with the formula m = V × ρ, where V is the block volume in m3 and ρ is density in kg/m3. U-blocks, if included in the calculation, are also added to the total exterior wall volume.
Loads. The estimated linear load on the foundation for exterior walls is calculated as the weight of the exterior masonry converted into gravitational force and divided by the total length of the load-bearing walls. For partitions, the calculation is carried out separately, and then the average pressure on the wall bearing area may also be determined.
U-blocks above openings
Top course. The number of U-blocks for the top bond beam course is determined by dividing the length of the load-bearing walls by the effective length of one U-block. The result is rounded up, and then the waste allowance is applied.
Lintels. For U-blocks above windows and doors, the calculator uses a separate logic. For each opening, its width is taken and a bearing length of 250 mm is added on each side, so the effective lintel length is b + 500 mm. This length is then divided by the length of one U-block and rounded up separately for each opening.
Final U-block quantity. The U-blocks of the top course and the U-blocks above openings are calculated as separate items. This is important because their purpose and quantity are not the same, and lintels depend on the dimensions of each specific window and door.
Reinforcement
Reinforcement spacing. If reinforcement is enabled, the calculator determines the number of reinforced courses according to the selected spacing N. The first course is included in the calculation, and then every next course at the specified interval. The number of such courses is determined step by step over the wall height.
Reinforcing bars. For bar reinforcement, the calculator takes the total length of the reinforced courses and multiplies it by the number of bars in one course. If opening deduction is enabled, reinforcement below windows is added separately according to the rule b + 1000 mm, which means 500 mm extra on each side of the window opening.
Reinforcement weight. The weight of steel reinforcement is determined from its length, diameter, and the steel density of 7850 kg/m3. This gives the estimated weight of the bars to be purchased for exterior walls and, if selected separately, for partitions.
Mesh. If reinforcing mesh is selected instead of bars, the calculator does not calculate weight, but the strip length and its area. The mesh area equals the total length of all reinforcing strips multiplied by the wall or partition thickness.
Joint length and adhesive consumption
Horizontal joints. The total length of horizontal joints is determined as the wall length multiplied by the number of horizontal joints between the courses. For exterior walls, this is L × (N - 1), and when a top U-block course is used, one more horizontal joint is added along the length of the load-bearing walls.
Vertical joints. Vertical joints are calculated from the lengths of the individual masonry sections. For each section, the calculator determines how many blocks fit into one course, then takes the number of vertical joints as the number of blocks minus one, multiplies it by the number of courses and by the block height according to the selected geometry.
Dry adhesive consumption. The estimated dry adhesive consumption is taken as 25 kg per 1 m3 of masonry. For exterior walls and partitions, it is calculated separately from the masonry volume after deducting openings and including the waste allowance.
Adhesive only for horizontal joints. The calculator also shows a separate estimate of which part of the adhesive consumption relates only to horizontal joints. This value is determined in proportion to the share of the horizontal joint length in the total length of horizontal and vertical joints.
Practical guidelines
Adhesive joint thickness. In the calculator, thin-joint masonry with a joint thickness of about 2-3 mm is often used. When the joint becomes thicker, the calculated wall height by courses increases and the estimated dry adhesive consumption changes.
Block sizes. Common sizes for exterior walls are about 600 × 300 × 200 mm or close to them. For partitions, blocks of the same length and height but with a smaller thickness, for example 75-150 mm, are often used.
Density. For foam concrete blocks, ranges of about 300-1000 kg/m3 are often used depending on the intended application. For low-rise exterior walls, structural-insulating grades are common, where load-bearing capacity and thermal performance requirements should be checked separately in the project.
Waste allowance. In practice, a waste allowance for cutting, breakage, and local losses is often taken in the range of 3-10% depending on the complexity of the layout, the number of openings, and the masonry experience. With simple geometry the allowance is usually smaller, while with many junctions and non-standard sections it is larger.
Related European standards
Masonry made of masonry units. The calculation logic is related to the general principles of masonry design according to Eurocode 6 EN 1996-1-1 and the execution rules in EN 1996-2. These documents are important for checking load-bearing capacity, detailing requirements, and workmanship quality, but the calculator itself is intended for a preliminary material estimate.
Mortars and masonry adhesives. Adhesive and mortar work is generally linked to EN 998-2, which covers masonry mortars. The actual adhesive consumption in a real project depends on block flatness, the type of mix, the shape of the notched tool, and the manufacturer's requirements.
Concrete masonry units. For dimensions and general requirements for concrete masonry units, EN 771-3 is used. If products of a specific manufacturer made of foam concrete or cellular concrete are used, their dimensional tolerances, strength, and density should be checked against the technical documentation for that exact block.
FAQs
Why is the block quantity calculated by area rather than by wall volume?
This approach matches real masonry work by courses more closely. The foam block calculator first determines the masonry area and then divides it by the face area of one block, so the result is convenient for piece-based purchasing.
Why calculate the block volume separately if the quantity in pieces is already known?
Volume is needed for ordering material in m3, arranging transport, and estimating weight. In addition, many suppliers of foam concrete blocks state shipment quantities and prices both in pieces and in cubic metres.
Why is the final block quantity always rounded up?
A block cannot be purchased as a fraction, so after dividing the masonry area by the area of one block, the result is always rounded up. This is a standard and safe principle for a preliminary foam block quantity calculation.
How accurate is the adhesive calculation for foam blocks?
The calculator gives an estimated dry adhesive consumption based on a specific value of 25 kg per 1 m3 of masonry. The actual consumption may differ because of block dimensional accuracy, joint thickness, workmanship, and the requirements of the adhesive manufacturer.
Can this calculation be used for foundation design?
The calculator shows the estimated weight and linear loads from the blocks, which is useful for a preliminary assessment. For final foundation design, a full building calculation, permanent and variable loads, ground properties, and verification according to the applicable European standards are required.