Work out how many cinder blocks you need for a wall. In Australia these are usually called besser blocks. Enter your wall and pick your block, and you get the full and half block count, mortar, core fill, pallets and a drawing of your courses.
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This cinder block calculator is set up for Australian blocks, walls measured in metres and a 10 mm mortar joint. It counts full and half blocks, then adds everything else that goes with them.
Prices stay optional. Add yours to see the cost of each line and a total. For a full job with footings and concrete, see the Concrete Material Cost Calculator.
People searching for a cinder block calculator in Australia usually mean the grey hollow block used for retaining walls, sheds and subfloors. The name changes depending on where you are.
| Name | Where It Is Used | What It Means |
|---|---|---|
| Besser block | Australia | The everyday name for a hollow concrete block |
| Grey block | Australia | The trade name for plain concrete blocks |
| Cinder block | United States | Traditionally a block made with cinders as aggregate |
| Breeze block | United Kingdom | A British name for a similar block |
| CMU | Technical documents | Concrete masonry unit |
Wikipedia describes cinder blocks as blocks made with cinders, meaning fly ash or bottom ash, as aggregate. The "besser" name comes from the Besser company, which made block machines. Apex Masonry traces the name to the company's early machine from 1904, and says the word stuck in Australia even after other firms started making blocks.
When you ring a supplier here, ask for besser blocks, grey blocks or concrete blocks, and give the series number. Asking for cinder blocks may get you a confused pause. This page uses both names, because they are the same job on site: a hollow block laid in mortar.
Concrete blocks suit jobs where a wall needs to be strong, fire resistant and quick to build from standard units. Wikipedia lists load-bearing walls with steel, crawl space foundations, retaining walls and fire-rated internal walls among the common uses. In Australia, you will see them in sheds, garages, subfloor walls, fences and garden walls.
| Job | Usual Block To Ask About | What To Check First |
|---|---|---|
| Low garden wall | 100, 150 or 200 series | Footing and control joints |
| Fence or screen wall | 150 or 200 series | Wind loads, footing and council rules |
| Shed or garage wall | 200 series | Plans, reinforcement and approvals |
| Subfloor wall | 200 series | Plans, footing and damp protection |
| Retaining wall | 200 or 300 series, core filled | Engineer design and drainage |
The block column is only a starting point for a chat with your supplier or builder, not a design. The block has to match your plans, so check them before you order. A wall built from the wrong series is an expensive thing to pull down.
Australian blocks are named by their series. The Concrete Masonry Handbook from the Concrete Masonry Association of Australia describes series of 100, 120, 150, 200 and 300 mm nominal width, and calls the 200 series the most common. The first number on a block is its series, so 20.01 is a standard block in the 200 series.
| Block | Actual Size | Width Of Wall | Default Weight | Default Pallet |
|---|---|---|---|---|
| 200 series 20.01 | 390 × 190 × 190 mm | 190 mm | 13.29 kg | 108 |
| 200 series 20.48 | 390 × 190 × 190 mm | 190 mm | 12.2 kg | 108 |
| 150 series 15.01 | 390 × 190 × 140 mm | 140 mm | 10.88 kg | 144 |
| 100 series 10.01 | 390 × 190 × 90 mm | 90 mm | 9.5 kg | 162 |
| 300 series 30.48 | 390 × 190 × 290 mm | 290 mm | 14.7 kg | 72 |
Default weights and pallets come from the National Masonry list dated 1 September 2026, except the 20.48 block, which comes from the BCP Masonry brochure. The 150 series figure is from an unnamed row of that size on the National list.
Weights vary much more than sizes do, because makers use different mixes. A standard 20.01 block is listed at 11.3 kg by BCP, 13.29 kg by National Masonry and about 16.2 kg by Midland Brick. That is a big difference across a pallet, so use your supplier's figure. The Block Weight line changes to suit. A half block weighs a bit more than half, and the calculator allows 55% of a full block, based on the National list.
A standard wall face is built from a few common shapes. Half blocks finish the ends, three-quarter and quarter blocks help with odd lengths, and lintel or knock-out bond beam blocks form a reinforced course. The calculator only counts full and half blocks, so ask your supplier about specials once your plans are set.
Each block takes up its own size plus a 10 mm joint, so a 390 × 190 mm face becomes a 400 × 200 mm module. That is where the standard count comes from.
| Step | Sum | Example: 12 m × 1.8 m Wall |
|---|---|---|
| Courses | Wall Height ÷ 0.2, rounded up | 1.8 ÷ 0.2 = 9 courses |
| Wall area | Run × Courses × 0.2 − Openings | 12 × 9 × 0.2 = 21.6 m² |
| Blocks in the wall | Wall Area × 12.5 | 21.6 × 12.5 = 270 blocks |
| Half blocks | Stopped Ends × Courses ÷ 2 | 2 × 9 ÷ 2 = 9 half blocks |
| Full blocks | Blocks − Half Blocks ÷ 2 | 270 − 4.5 = 265.5 |
| To buy | Each count × (1 + Waste %), rounded up | 279 full and 10 half |
Blocks are laid in stretcher bond, with each course offset by half a block. At a square end, every second course must finish with a half block. A wall with two stopped ends needs about one half block per course. Two half blocks take the place of one full block, so the calculator takes that off the full count. Set Stopped Ends to 0 where a wall runs into another wall or goes around a corner.
When walls meet, the corners would be counted twice if you used the outside perimeter. So the Four Walls option uses the centreline run instead.
For a 9 m × 6 m outline in 200 series, that is 2 × 15 − 4 × 0.19 = 29.24 m. Corners are bonded, so this option adds no half blocks for stopped ends. Add some for each door or window opening.
You cannot lay a part of a course without cutting blocks, so the calculator rounds your height up to the next whole course. Enter 1.3 m and it will count 7 courses, or 1.4 m of wall. The Courses line shows you what will really be built, and the drawing matches it.
This table gives the blocks per metre of wall run for standard 400 × 200 mm block modules, before waste and half block changes. Multiply by your wall length.
| Wall Height | Courses | Blocks Per Metre | Blocks For 6 m | Blocks For 12 m |
|---|---|---|---|---|
| 0.6 m | 3 | 7.5 | 45 | 90 |
| 1.0 m | 5 | 12.5 | 75 | 150 |
| 1.2 m | 6 | 15 | 90 | 180 |
| 1.8 m | 9 | 22.5 | 135 | 270 |
| 2.4 m | 12 | 30 | 180 | 360 |
| 3.0 m | 15 | 37.5 | 225 | 450 |
Every metre of wall run at 2.4 m high is 30 blocks, which at 13.29 kg each is about 400 kg of block before any mortar or fill. Blocks add up fast, both on the truck and on your back.
These use 200 series 20.01 blocks and a 5% waste allowance, unless they say otherwise.
That is 6 courses and 7.2 m², or 90 blocks in the wall. With two stopped ends, it takes 6 half blocks and 87 full blocks. With waste you would buy 92 full and 7 half. The mortar comes to 0.12 m³, or 10 bags of 20 kg, and the blocks weigh about 1.27 tonnes. At the National Masonry price of $5.01 and $3.04, and a made-up $11 for each mortar bag, the materials come to $460.92 + $21.28 + $110.00 = $592.20. Using the Bunnings Trade block prices below, the same list is $976.23, which is why it pays to ring around.
That is 9 courses and 21.6 m². You would buy 279 full and 10 half blocks. Mortar is 0.36 m³, or 29 bags. Fully filled at 0.083 m³ per m², the core fill is 1.793 m³, or 1.972 m³ with a 10% allowance, so the order is 2.0 m³. The blocks weigh about 3.8 tonnes, on 3 pallets. If this wall holds back soil, it needs a design. The 1.8 m size here is only for the sum.
The centreline run is 29.24 m. With 12 courses, the gross area is 70.176 m², and taking off the openings leaves 63.876 m². That is 798.45 blocks, so you would buy 839 with waste, plus half blocks around the openings. Mortar is 84 bags, and full core fill is 5.9 m³. The blocks weigh about 11.2 tonnes and fill 8 pallets, so delivery and site access need planning.
Thinner blocks use the same module, so the area still counts at 12.5 per square metre. That is 27 m² and 337.5 blocks in the wall. You would buy 350 full and 10 half blocks, and 36 bags of mortar. At 10.88 kg each, the blocks weigh about 3.9 tonnes.
The Concrete Masonry Handbook gives about 1 m³ of mortar for every 800 blocks. Cement Australia's Trade Mortar sheet says a 20 kg bag covers 10 masonry blocks with a 10 mm joint. That product is rated M4 and described as conforming to AS 3700. Those two figures line up well, so the calculator shows both a volume and a bag count.
| Blocks | Mortar Volume | 20 kg Bags | Damp Sand If Site Mixed |
|---|---|---|---|
| 50 | 0.06 m³ | 5 | 0.08 m³ |
| 100 | 0.13 m³ | 10 | 0.15 m³ |
| 250 | 0.31 m³ | 25 | 0.38 m³ |
| 500 | 0.63 m³ | 50 | 0.75 m³ |
| 1,000 | 1.25 m³ | 100 | 1.50 m³ |
For a site mix, the handbook lists a 1 : 1 : 6 mortar, meaning cement, lime and sand. For 1 m³ of mortar it gives 6 bags of cement, 6 bags of lime and 1.2 m³ of damp sand, which allows for 20% bulking. It does not state the bag weight, so ask your supplier before relying on that bag count. The damp sand figure on the PDF uses the 1.2 m³ value. Our Concrete Mix Ratio Calculator also covers cement and sand mortar.
Blocks are normally laid with face shell bedding. The handbook describes mortar on the two face shells and the perpends, not on the webs. Most blocks have tapered cores and go in with the wider part of the face shell up. It also warns to discard mortar once it has started to set, and not to mix it again with water. It prefers an ironed joint for face blockwork and flush joints where a wall will be rendered, and says raked joints should not be used with hollow blocks.
A hollow block wall is often reinforced with steel in the cores, then filled with grout or a flowing concrete. Your plans say which cores get steel and which get filled. The Concrete Masonry Handbook gives these volumes.
| Block | Fill Per m² Of Wall | Fill Per 100 Blocks |
|---|---|---|
| 15.01 or 15.42 | 0.054 m³ | 0.43 m³ |
| 20.01 or 20.42 | 0.083 m³ | 0.66 m³ |
| 20.48 | 0.100 m³ | 0.80 m³ |
| 30.48 | 0.180 m³ | 1.44 m³ |
The calculator uses these figures, and scales them in a straight line if you fill only part of the cores. The 100 series has no published figure in that table, so the fill box hides for that block. The handbook asks for at least 12 MPa, preferably 20 MPa, a cement content of at least 300 kg/m³ and 10 mm coarse aggregate. It says lifts over 2.4 m should be filled in two stages about 30 minutes apart, and lifts over 3 m should not go in one pour. Our Concrete Foundation Wall Calculator goes further on filling walls, including mix extras and what to tell the supplier.
Blocks work best when the wall fits the module, as that saves cutting. The handbook recommends planning in 200 mm or 400 mm steps, with the block length and height in mind.
| Item | Handbook Guidance |
|---|---|
| Course height | Nominal 200 mm, actual 190 mm, three courses in a 600 mm module |
| Piers and walls | 10 mm less than the module, such as 890 mm or 1,790 mm |
| Openings | 10 mm more than the module, such as 910 mm or 1,210 mm |
| Joint | 10 mm allowance per joint |
If your wall is 6.1 m long, try to make it 6.0 m less a joint. On the height side, working from the footing level up to the top of the wall in whole courses avoids a row of cut blocks. Corners should be set out first, with a string line for each course. Remember the actual top of a wall ends 10 mm under a full module, because there is no joint on the top course.
A cinder block calculator counts blocks, but a wall is only as good as what sits under it. Block walls are heavy, and a footing has to suit the wall height, the ground and any load. Your plans set the size, and the Concrete Footing Calculator works out the concrete. The handbook's example details show N12 starter bars at corners, beside openings and at a maximum of 1,800 mm centres, reduced for cyclonic areas. Your engineer sets the steel for your wall.
| Wall | Maximum Spacing |
|---|---|
| Unreinforced, articulated residential | 6 m |
| Unreinforced, other construction | 8 m |
| 90 and 110 mm walls | At points of weakness, up to 6 m apart |
| 140 and 190 mm walls with bond beams | Up to 8 m |
| Reinforced walls over 3 m high | 16 m |
| Reinforced walls up to 3 m with a top bond beam | Can be left out |
Source: Concrete Masonry Handbook, Concrete Masonry Association of Australia, which defers to AS 3700, AS 4773 and the Building Code of Australia.
Retaining walls need extra care. They hold back soil and water, and a block wall that looks fine at first can lean or fail later. Approval rules depend on your council. As one example, Brisbane City Council says a building application is needed where the wall height plus the retained fill or cut is over 1 metre, or where a wall is closer than 1.5 metres to a building or another retaining wall. Ask your own council or a certifier, and use an engineer for anything that holds back soil.
Block prices differ a lot between sellers. These examples are for a standard 200 series block.
| Seller | Full Block | Half Block | Note |
|---|---|---|---|
| National Masonry list | $5.01 | $3.04 | Brisbane and Gold Coast, 1 September 2026 |
| Midland Brick | $5.66 | Not checked | Includes GST, excludes cartage, $509.09 a pallet |
| Bunnings Trade and Bunnings | $9.08 | $4.41 | Brighton Masonry, checked November 2026 |
The gap is large, and it may reflect pallet buying, region and delivery. Single blocks from a hardware store cost more, but you can pick up a few at a time. A masonry yard usually wants full pallets. Midland Brick says its blocks are supplied on pallets only, and that the pallet charge is refundable on return.
Plan the delivery too. Pallets are heavy, and each 108-block pallet of 13.29 kg blocks weighs about 1.4 tonnes. Check that the truck can reach the site and that the ground will hold the load. Set the pallets close to the wall to cut down on carrying.
A full block can weigh more than 13 kg, so plan safe lifting and take regular breaks. Mortar and wet concrete can burn skin, and cutting blocks creates dust containing silica. Wear suitable gloves, eye protection and boots, and read Safe Work Australia's silica guidance before you cut.
Multiply the wall length by its height to get the area in square metres, then multiply by 12.5 for standard blocks. A 6 m × 1.2 m wall is 7.2 m², or 90 blocks before waste. Then add an allowance for breakages and cuts.
Standard Australian blocks use 12.5 per square metre of wall. That comes from a module of 400 mm long and 200 mm high, including the 10 mm mortar joints.
In everyday use, yes. Cinder block is the common American term, and besser block is the common Australian one. Strictly, a true cinder block uses cinders as aggregate, while Australian grey blocks are concrete masonry units.
The standard 200 series block is 390 × 190 × 190 mm actual, or 400 × 200 × 200 mm nominal with its 10 mm joints.
Published weights for a standard 20.01 block run from about 11.3 kg to 16.2 kg, depending on the maker and mix. Check the figure from your supplier, and change the weight in the calculator to match.
Published pallets for a standard 200 series block hold 90 or 108 blocks. It varies by maker, so ask your supplier. The pallet may also carry a refundable charge.
The Concrete Masonry Handbook gives about 1 m³ of mortar per 800 blocks, so about 0.125 m³ per 100 blocks. Cement Australia says a 20 kg bag of Trade Mortar covers 10 masonry blocks, so that is about 10 bags.
For fully filled 20.01 blocks, the Concrete Masonry Handbook gives 0.083 m³ per square metre of wall, or about 0.66 m³ per 100 blocks. Other block types differ, and the calculator has the published figures.
Yes. The calculator starts at 5%, which matches a Midland Brick note that up to 5% of blocks may chip or break in handling. Cuts around openings can use more.
A block wall needs a suitable footing. The size depends on the wall, the ground and the loads, so follow your plans. Our Concrete Footing Calculator works out the concrete once you have the sizes.
Long walls usually do. The Concrete Masonry Handbook gives a maximum of 6 m for unreinforced walls in articulated residential construction, and 8 m in other construction. Your plans set the actual locations.
No. Your numbers stay in your browser and nothing is uploaded. Use Download Wall Estimate to keep a copy.
Figures reviewed November 2026. Sources: Concrete Masonry Association of Australia, National Masonry, BCP, Midland Brick, Cement Australia, Bunnings, Brisbane City Council, Apex Masonry, Wikipedia and Safe Work Australia, linked in the sections above. Results are planning estimates and not a wall design, so confirm your final quantities and price with your supplier and the people responsible for your project. See our Disclaimer and Calculator Methodology.