Masonry
Calculate blocks and bonding material for masonry
How the calculation works
Enter the wall dimensions or area, openings, block type, joint width and reserve. The calculator subtracts openings, works out blocks per m² and adds the reserve.
Formula and assumptions
Blocks per m² = 1 ÷ ((length + joint) × (height + joint)), in metres. Blocks = effective area × blocks per m² × (1 + reserve), rounded up. Effective area = wall area − openings. Mortar and wall weight use the default assumptions in the app.
Worked example
Wall 10 m² with no openings, block 25 × 19 cm, 1 cm joint: 1 ÷ (0.26 × 0.20) = 19.23 blocks/m². 10 × 19.23 = 192.3; with 5 % reserve → 201.9 → 202 blocks.
What affects real consumption
- Real joint width and bonding pattern (head joints).
- Breakage and cutting at openings and corners.
- Deviation of block dimensions from nominal.
Frequently asked questions
Should I add a reserve for blocks?
A few percent is usual for breakage and cutting; you set the reserve value yourself.
Is wall thickness taken into account?
Thickness is part of the chosen block and is used to estimate wall weight, while blocks per m² depend on length, height and joint.