Concrete Block Sizes Explained: 100, 150, 200, 300 & 400 Series

Block size is one of those details that quietly shape a whole project, affecting structural strength, build time, and cost. Pick a block that's too light for the load, and you create problems. Pick one heavier than you need, and you spend more than necessary. 

This guide explains the standard concrete block sizes used in Australia, from the 100 series up to the 400 series, with dimensions, uses, and practical guidance to help you plan and order with confidence.

Australian Standard Block Sizes (Quick Reference)

First, a quick word on how block sizing works, because it trips a lot of people up. Concrete blocks are made to a face of 390 x 190mm, which is the actual, or work, size. Laid with a standard 10mm mortar joint, each block takes up a nominal 400 x 200mm of wall. 

The series number (100, 150, 200, 300, 400) refers to the nominal width of the block. So a 200 series block measures 190mm wide in your hand and 200mm nominal once you allow for the joint.

Here's the full range at a glance:

 

 

Because every series shares the same 390 x 190mm face, the blocks-per-square-metre figure is the same right across the range, about 12.5 (often rounded to 12 or 13). The width changes the wall's thickness and strength, not how many blocks cover a square metre. 

Weights vary by manufacturer and whether the block is solid or hollow, so treat the weight column as a general guide rather than an exact figure.

 

100 Series Blocks

At 390 x 190 x 90mm, the 100 series block is the lightest and thinnest in the range. It's a non-structural block, used for things like partition walls, garden edging, and other low-load jobs. It's easy to handle, but it isn't suitable for structural or retaining walls, so keep it away from anywhere where strength matters.

150 Series Blocks

The 150 series measures 390 x 190 x 140mm and steps the strength up a notch. It suits light internal walls and low-load structural work. It's stronger than the 100 series, but still limited for heavy loads, so it sits comfortably in the middle of the range.

200 Series Blocks (the Most Common)

The 200 series, at 390 x 190 x 190mm, is the workhorse of Australian block construction and the most widely used concrete block size by a wide margin. The 200 series block dimensions make it ideal for structural walls, retaining walls, boundary walls, and foundations.

Its hollow cores take steel reinforcement and concrete core fill, which is exactly what gives a 200 series wall its strength. You'll also find it in a few handy variations: standard blocks, H blocks (open at both ends to make reinforcing easier), and half blocks for finishing the ends of courses neatly. 

If you're planning a retaining wall, our guide on how to build a block retaining wall shows where these blocks fit into the build. Pallet quantities vary by manufacturer, so confirm before ordering.

300 Series Blocks

The 300 series, at 390 x 190 x 290mm, brings more thickness and more strength. The 300 series block dimensions suit commercial construction, high retaining walls, and the ground floors of multi-storey buildings, where greater load capacity is needed. The extra mass also means heavier handling on site, so factor that into your planning.

400 Series Blocks

The 400 series is the heavy hitter at 390 x 190 x 390mm. This 400 series block is built for heavy-duty structural work like lift shafts, industrial builds, and tall retaining walls. It offers maximum thickness and strength, and walls using it almost always require engineering.

How Block Size Affects Your Project

Concrete block size isn't only about strength. Larger blocks cover more wall, so the wall goes up faster with fewer joints and more strength, but each block is heavier to handle. Smaller blocks are easier to lift and more flexible for tight or detailed work, though you'll lay more of them. The right choice balances wall height, structural load, and budget.

How to Choose the Right Block Size

Matching concrete block sizes to the job usually comes down to a simple shortlist:

• 100 series for non-structural partitions and edging
  
  
• 150 series for light internal walls
  
  
• 200 series for most residential builds, retaining walls, and general structural work
  
  
• 300 or 400 series for commercial work, heavy structural builds, and high retaining walls

When in doubt, or whenever an engineer is involved, follow the spec for your specific wall.

Blocks per Pallet and Ordering Tips

Blocks are sold by the pallet, and quantities vary by concrete block size and manufacturer. As a rule, the larger the block, the fewer fit on a pallet, so a pallet of 300 series holds fewer than a pallet of 200 series. 

Always confirm the pallet quantity with the supplier before ordering, and order a little extra to cover cuts and breakages. If you're still choosing between block and brick for the job, our besser blocks vs bricks comparison can help.

Buy Concrete Blocks Online at BBPO

Once you know the size you need, ordering is simple. For the full picture on block types and uses, start with our complete guide to blocks. BricksBlocksPaversOnline stocks a full range of blocks for DIY, builder, and commercial projects, with delivery across the country. 

The grey concrete blocks range covers the besser block sizes most builds rely on, from the everyday 200 series up. Enter your postcode to see pricing for your area and order exactly what your project needs.