How Many AAC Blocks per Square Metre? Q-Con, Concrete Block and Clay Brick
Figures reviewed 14 October 2026
Walls in Thailand
Many Thai houses use a reinforced concrete frame with infill walls made from one of these materials:
AAC (autoclaved aerated concrete) blocks, often called by the brand name Q-Con or by the Thai term "it muan bao" (lightweight block). These are 20 × 60 cm on the face.
Hollow concrete blocks.
Small red clay bricks ("it mon").
The number you need per square metre depends on the size of the face you see on the wall and on the thickness of the joints.
Units per m² = 1 ÷ [(unit length + joint) × (unit height + joint)], in metres.
| Unit (face length × height) | Joint | Units per m², before waste |
|---|---|---|
| AAC 60 × 20 cm | none (the figure sellers quote) | 8.33 |
| AAC 60 × 20 cm | 3 mm (thin-bed adhesive, example) | 8.17 |
| AAC 60 × 20 cm | 10 mm (illustrative conventional mortar case) | 7.81 |
| Concrete block 39 × 19 cm | 10 mm | 12.5 |
| Clay brick, example 15 × 4 cm face | 10 mm | 125 |
Clay bricks vary from factory to factory. Measure a real brick and put its dimensions into the formula instead of relying on the 125 example.
Why 8.33 and 7.81 are both "right"
Sellers quote 8.33 because it's simply 1 ÷ (0.6 × 0.2), with no allowance for joints. The calculator adds the joint to each block's size, so it gives a slightly lower number. Once you add an allowance for cutting around doors, windows and columns, the amount you actually buy usually ends up close to 8.33 or above.
Example: AAC wall 5 × 2.4 m with one door
Wall area = 5 × 2.4 = 12 m²
Subtract the door opening (2 m²) → 10 m² net
Area of one block with joints = 0.61 × 0.21 = 0.1281 m²
10 ÷ 0.1281 = 78.06 blocks
Add 10% → 85.87 → 86 blocks
With thin-bed adhesive and 3 mm joints, the count before waste is about 82 blocks. Use the joint thickness from the instructions for the system you're actually using.
Don't mix up the faces
Measure the face that shows on the wall, not the block's thickness. A 20 × 60 cm AAC block is often 7.5 cm or 10 cm thick, and the thickness only sets how thick the wall is. If you enter 7.5 cm as the block height by mistake, the count comes out nearly three times too high.
What the block count leaves out
These are bought or calculated separately:
Conventional mortar: use the mortar calculator where its assumptions fit. For thin-bed AAC adhesive, use the selected manufacturer’s coverage instructions instead.
Rendering (plaster) over the finished wall.
Lintels over openings and stiffener columns in long walls.
Wall ties into the concrete frame.
Half blocks and cut pieces needed by the real laying pattern.
Load-bearing walls, or walls with fire or acoustic requirements, should be checked by a qualified builder or engineer before you place a final order.
FAQ
Do I subtract small openings? You can subtract their area, but small openings mean more cutting and more waste, so don't lower your waste allowance at the same time.
Is mortar included in the result? No. The mortar calculator can help with applicable conventional joints; thin-bed AAC adhesive needs the product’s own coverage data.
How do I order by the pallet? Divide the number of blocks you need by the number of blocks per pallet for that product, round up, and ask whether the shop sells part pallets.
Estimate blocks with 10 mm joints