AAC Block Sizes: Standard Dimensions in mm

The most common AAC block size is 600 mm long and 200 or 250 mm high, with widths (wall thicknesses) from 100 to 300 mm. China’s GB/T 11968-2020 lists 600 mm length, 200–300 mm heights and 100–300 mm widths; India’s IS 2185 (Part 3) uses nominal sizes that include the joint; Dubai’s DMS 1 Part 3 lists work sizes of 390–590 mm length.

Size is not only a catalog question. It decides the joint type, the tolerance class the cutting machine must hold, and how much of each cake is offcut. This guide sets out the sizes and tolerances in each standard, the sizes used in the UAE, and what they mean for the cutting line.

AAC Block Standard Size Chart (mm)

Two things stand out. Outside the UK, the 600 mm length (or 590 mm plus a 10 mm joint) is the common thread, although IS 2185 also lists 400 and 500 mm. And width is the size buyers really choose, because it is the wall thickness.

UK and European examples

The UK is the main exception to the 600 mm rule. UK aircrete blocks such as H+H’s High Strength Celcon block are 440 × 215 mm on the face, so that with 10 mm joints one block (450 × 225 mm) matches two brick lengths and three brick courses. Note that EN 771-4 does not cover storey-height panels.

GB/T 11968-2020 Sizes and Tolerances

GB/T 11968-2020 lists a length of 600 mm, widths of 100, 120, 125, 150, 180, 200, 240, 250 and 300 mm, and heights of 200, 240, 250 and 300 mm. The 2020 edition introduced two product types by dimensional accuracy. The size list above and the tolerances below are as cited in the T/CASME 2022 draft group standard (Tables 1 and 2), which is built on GB/T 11968-2020; check the current edition of GB/T 11968 before writing them into a contract.

Type I blocks are meant for thin-bed adhesive, where the joint is only a few millimeters and cannot absorb size differences. Type II blocks are laid with conventional mortar. Our reference line cuts to ±3 mm in length and ±1 mm in width and height, which is the Type I tolerance. Other sizes are commonly produced by agreement; check the current edition for what the standard says about non-listed sizes.

EN 771-4: Declared Sizes and Tolerance Categories

EN 771-4 does not specify standard sizes. The manufacturer declares length, width and height in mm, and one of three tolerance categories:

Dimensions are measured to EN 772-16 and flatness to EN 772-20. A manufacturer can declare closer tolerances than the category. TLMB is the tightest: ±1.0 mm in height plus 1 mm flatness is what lets a thin-bed wall go up course after course without packing. The GCC adopted EN 771-4:2011 as GSO EN 771-4:2021, so these categories also apply to suppliers declaring to the Gulf standard. Our EN 771-4 guide covers the rest of the standard.

IS 2185 (Part 3): Nominal vs Actual Size

India’s IS 2185 (Part 3):1984 (reaffirmed) refers to blocks by nominal dimensions that include the mortar joint:

• Nominal length 400, 500 or 600 mm; height 200, 250 or 300 mm; width 100, 150, 200 or 250 mm
• Half-length blocks of 200, 250 or 300 mm
• Actual dimensions 10 mm less than nominal, or 6 mm less where finer jointing is specified
• Tolerances of ±5 mm on length and ±3 mm on height and width

So a “600 × 200 × 200” IS 2185 block is actually 590 × 190 × 190 mm when made to the 10 mm rule. A draft revision text posted on the BIS portal adds a 625 mm length and widths from 50 to 300 mm, and carries an editorial note that industry commonly makes blocks to the nominal rather than the actual dimensions. Check whether a revised edition has been issued before quoting it.

Standard AAC Block Size in the UAE and the Gulf

In Dubai, AAC masonry units are covered by Dubai Municipality’s DMS 1: Part 3: 2014. Its Table 1 lists the most frequently used work sizes, with tolerances measured to BS EN 772-16:

Other work sizes may be used. The manufacturer declares the actual dimensions, and the purchaser specifies the work size. A 590 mm work size plus a 10 mm joint gives a 600 mm coordinating length, and 390 mm gives 400 mm. The same standard sets a minimum average normalized compressive strength of 3.2 N/mm², a maximum declared gross density of 850 kg/m³ and drying shrinkage of no more than 0.9 mm/m.

Across the GCC, the regional product standard for AAC masonry units is GSO EN 771-4:2021, which uses declared sizes and the GPLM, TLMA and TLMB tolerance categories above. In Saudi Arabia, note that SASO 2875:2024 (the document on the SASO site is marked draft) covers lightweight non-load-bearing units made of foamed concrete, lightweight aggregate concrete and polystyrene concrete; its scope does not name autoclaved aerated concrete. A plant serving several Gulf markets should confirm the standard each buyer is specifying before fixing its size range.

How AAC Block Sizes Are Cut from the Cake

On a tilting line, all sizes come from one cake. On our reference line the net cake is 4,200 × 1,200 × 600 mm. After tilting it stands on its side plate: 4.2 m long, 1.2 m high and 0.6 m thick. The lengthwise cut uses horizontal wires to set the block height and vertical wires to set the width, and the crosswise cut puts a vertical wire every 600 mm to set the block length, so each row gives seven 600 mm blocks.

That makes some sizes much more efficient than others. The table below is an illustrative calculation from the reference cake dimensions only; it ignores trimming allowances and wire kerf, and the actual cutting plan is set with the line supplier.

A plant that sells mostly 600 × 250 × 250 mm blocks will either cut a second size in each cake or plan its product mix around it. On our reference line, cutting offcuts and waste slurry go back to batching, so offcut is lost capacity rather than lost raw material. The AAC block cutting machine article explains the cutting sequence.

Choosing Sizes for a New AAC Plant

1. Start with the standard your buyers specify. GB/T 11968, EN 771-4 (or GSO EN 771-4), IS 2185, or DMS 1 Part 3 in Dubai; each has a different size and tolerance logic.
2. Decide the joint type. Thin-bed markets need Type I or TLMB-level tolerances; conventional-mortar markets accept Type II or GPLM.
3. Fix the wall thicknesses. Width is the size buyers argue about. List the widths your market uses and check how they divide the cake.
4. Check density and strength together with size. Strength minimums such as Dubai’s 3.2 N/mm² apply to every size you sell. See AAC block density.
5. Plan packing. On our reference line each mold is split into two stacks of about 1.5 m³ on pallets with three straps, handled by clamp forklifts; your size mix decides how many blocks are in a stack.

FAQ

What is the standard size of an AAC block in mm?

The most common size is 600 × 200 mm on the face, with widths of 100, 150, 200, 250 or 300 mm, for example 600 × 200 × 200 mm. GB/T 11968-2020 lists 600 mm length, 200–300 mm heights and 100–300 mm widths. EN 771-4 has no standard sizes, and UK blocks are usually 440 × 215 mm.

What is the standard AAC block size in the UAE?

Dubai Municipality’s DMS 1: Part 3: 2014 lists the most frequently used work sizes as 390–590 mm long, 200–250 mm high and 100, 150, 200 or 250 mm wide, with tolerances of ±3 mm on length and ±2 mm on width and height. Other sizes may be used, and the manufacturer declares the actual dimensions.

What is the tolerance on AAC block dimensions?

It depends on the standard. GB/T 11968-2020 Type I allows ±3 mm length and ±1 mm width and height; Type II ±4 and ±2 mm. EN 771-4 TLMB allows ±1.5 mm length, ±1.0 mm height and ±1.5 mm width. IS 2185 (Part 3) allows ±5 mm length and ±3 mm height and width.

Why are some AAC blocks 590 mm or 625 mm long instead of 600 mm?

A 590 mm work size plus a 10 mm mortar joint gives a 600 mm coordinating length, which is how IS 2185 (Part 3) and Dubai’s DMS 1 Part 3 express size. A 625 mm length appears in a draft revision text on the BIS portal, but not in the 1984 edition of IS 2185 (Part 3), so check which edition your buyer specifies.

Which AAC block size is best for walls?

Choose the width for the wall’s job: thinner blocks for internal partitions, thicker ones where thermal, acoustic or fire performance or a load-bearing design calls for it. The local code and the designer set the thickness. Keep the face size your market’s masons and lintels are built around, usually 600 × 200 mm.

Planning an AAC Block Plant?

Your size range and tolerance class shape the cutting machine and the packing line. See our AAC block production line for the process and product range, and the AAC block plant setup guide for the full planning sequence.

Sources

• GB/T 11968-2020, Autoclaved aerated concrete blocks (China) — SAMR national standards catalog entry
• T/CASME draft (2022), Table 1 sizes and Table 2 size tolerances (Type I / Type II), built on GB/T 11968-2020 — National Group Standards Platform
• EN 771-4:2011+A1:2015, Autoclaved aerated concrete masonry units — CEN catalogue entry (iTeh)
• EN 771-4:2003/A1:2005, sample with Table 2 limit deviations — iTeh
• GSO EN 771-4:2021 — GCC Standardization Organization
• IS 2185 (Part 3):1984 — Bureau of Indian Standards
• IS 2185 (Part 3):1984, text — Internet Archive
• IS 2185 (Part 3) draft revision text — Bureau of Indian Standards portal
• DMS 1: Part 3: 2014, Autoclaved aerated concrete masonry units — Dubai Municipality
• SASO 2875:2024 (draft), lightweight non-load-bearing concrete units — Saudi Standards, Metrology and Quality Organization
• H+H UK, High Strength Celcon Block declaration of performance