Aerated concrete block calculator
Aerated concrete blocks are large and light, laid with a thin bed of adhesive. The number of blocks depends only on the wall face and the block face — the thickness is chosen for the role of the wall.
Your measurements
Result
- Net wall area
- 13.60 m²
- Area to order (incl. waste)
- 14.28 m²
- Blocks needed
- 96 pcs
- Thin-bed adhesive (approx.)
- 71 kg
The block thickness doesn't change the number of blocks per m² — choose it by the role of the wall.
How the calculation works
- Net area = total wall length × height, minus door and window openings.
- Area to order = net area + 5% waste (10% for walls with many corners or openings).
- Blocks = area to order ÷ face of one block (60 × 25 cm = 0.15 m²), rounded up.
- Adhesive = area to order × about 5 kg/m².
Worked example
A wall 6 m long and 2.6 m high is 15.6 m²; minus 2 m² of openings leaves 13.6 m². With 5% waste you order 14.28 m², which is 14.28 ÷ 0.15 = 96 blocks of 60 × 25 cm and about 71 kg of adhesive (3 bags of 25 kg).
What the calculator assumes
- Block thickness (10–30 cm) doesn't change the number per m²: 25–30 cm is typical for external walls, 10–15 cm for partitions.
- 5 kg/m² corresponds to a ~25 cm wall laid with 1–3 mm thin-bed adhesive (about 20 kg per m³ of masonry).
- The first course is set on ordinary mortar to level it; the rest with adhesive.
When to adjust the result
- Blocks are sold by the pallet, by volume: divide the wall volume by the m³ per pallet given by the manufacturer.
- Lintels, ring beams and concrete columns take up part of the wall area — a project deducts them separately.
Building with aerated concrete blocks
Precision blocks are laid with thin-bed mortar (a few millimetres), which is faster and reduces thermal bridging, but it needs a perfectly level first course. Set that course on a normal mortar bed over a damp-proof course and check it in every direction before continuing.
Cut blocks with a hand saw or a band saw, and use the system's U-blocks for ring beams and lintels. Aerated blocks hold fixings poorly with ordinary plugs, so use plugs designed for them. Outside, the blocks must be rendered or clad because they absorb water.
Frequently asked questions
How many aerated concrete blocks per m²?
With a 60 × 25 cm face, 6.67 blocks per m² before waste; with 5% waste, about 7.
Mortar or adhesive for aerated concrete?
Thin-bed adhesive for all courses except the first, which is bedded in mortar to get it perfectly level.
Do aerated block walls need insulation?
Thick, low-density blocks can meet some energy targets alone; thinner or denser blocks usually need external insulation. Check the wall's U-value.
Can I use normal mortar with aerated blocks?
Only for the first levelling course; the rest should use thin-bed mortar, otherwise joints become thermal bridges and the wall is less accurate.