Block Calculator

A 600 × 200 × 100 mm block covers 0.12 m², so a square metre takes 8.33 blocks, and with a 2 mm thin joint the practical figure is about 8.5. A 390 × 190 mm block covers less and needs closer to 13. The calculator derives the count from the block you enter rather than from a nominal size, because a 20 % error here becomes a pallet on site.

Thin-joint blocks are laid with adhesive rather than mortar, which changes both the joint and the accessory: about 25 kg of glue covers 10 to 12 m² of wall, and it is ordered separately from the blocks.

Aerated blocks come in thicknesses from 75 to 300 mm and the wall's thermal performance comes from that thickness, so the number of blocks per square metre stays the same while the volume doubles. If you are building a single-leaf wall, the thickness is the wall, not a multiple of blocks.

Openings are deducted from area, but lintels over them are not part of the block count. Every opening needs a lintel or a reinforced course, and those are counted per opening rather than per square metre.

Blocks are light but brittle: corners break in transit and offcuts crumble rather than cutting cleanly. A 3 to 5 % allowance covers the broken edges, and the first course should be laid on a full mortar bed or a levelling compound, because every subsequent course inherits its error.

Aerated block absorbs water quickly, so the adhesive needs the surface damp or the joint dries before it bonds. A spray bottle costs less than a failed course, and on a hot day it is not optional.