Motherboard Sizes Explained

Discover which among the motherboard sizes is the right one for you


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If you’re interested in building a PC in 2023, either for gaming or productivity, then you’re probably noticing that motherboard sizes and PC component sizes (and shapes) differ, which can be confusing for newcomers. Motherboard sizes are no different

In truth, once you do a little bit of digging, you’ll notice that lots of components are compatible with each other. Once you’ve settled on a CPU and motherboard pairing of the same socket type (for example the AM5 socket from AMD), and the required RAM for the motherboard, then putting together a PC is much, much simpler than one might think. Some people even go as far as comparing it to playing with a LEGO set. On that note, let’s take a look at the different motherboard sizes, the pros and cons of each, and what size would best suit your particular needs.

You’re likely already familiar with the term ATX, which comes up a lot when people are talking about motherboards. But what does ATX mean? ATX is an Intel-coined term and stands for Advanced Technology eXtended. It refers to an industry standard when it comes to motherboard and power supply compatibility and has later incorporated PC cases. By getting everyone to use a standard form factor when manufacturing a component, the PC market became more diverse and accessible to a larger audience. 

Today, we have a big number of industry-standard motherboard sizes, each of them having similar features, advantages, and drawbacks. Let’s start by taking a look at everyone’s favorite, the ATX form factor.


 ATX Motherboard
ATX Motherboard

A full-size ATX board has a height of 305mm and a width of 244mm, or 12 x 9.6 inches. When you’re planning a build, if you’re picking up an ATX motherboard, you’re going to want to pair it with an ATX-compatible PC case. These can either be super-towers, full-towers, middle-towers, or mini-towers. As long as they’re built to support the ATX format, then the board will fit 10/10 times.

The ATX board is built for running all sorts of systems. With at least four RAM DIMMs, it can support dual or quad-channel memory, giving the user better performance in specific applications over a board that doesn’t support this type of configuration.

ATX boards typically have seven expansion slots, allowing you to run up to four GPUs with Nvidia SLI or AMD Crossfire if your case and power supply are fit to power and house such a system. Moreover, the large number of expansion slots allows users to install quality-of-life upgrades, like a better network card that can even support WiFi, Bluetooth adapters, sound cards, USB hubs, and more. 

This type of motherboard usually provides manufacturers with enough space to install big heatsinks, an intricate VRM (voltage regulator module, we’ll explain later), a bigger rear IO, and more SATA and USB header connectors, giving you a better experience.

This type of motherboard is powered by a 24-pin connector with a 6/8-pin connector for the CPU, allowing you to run high-end processors, and even overclock the processors on unlocked motherboards. P

  • Have a complete IO
  • Plenty of room for heatsinks
  • Good VRM compared to the smaller boards
  • Can’t fit into compact form-factor cases
  • More expensive than mATX and mini-ITX motherboards

Extended ATX (EATX)

EATX Motherboard example
EATX Motherboard example

Extended ATX boards are slightly bigger ATX boards – I know, kind of anticlimactic. These boards are slightly bigger, measuring 305x330mm (12 x 13 inches rather than 12 x 9.6), giving you more connectors. They sometimes have dual-socket support, allowing you to run two CPUs using the same board, but that’s not always the case.

  • Some support dual sockets
  • Some have more RAM DIMMs
  • More connectors
  • Fewer products on the market
  • Can’t fit in some PC cases
  • More expensive without adding any real value


Unlike the other featured motherboard sizes, XL-ATX boards do not abide by a standard height and width. XL-ATX boards are very rare, with only a handful of manufacturers releasing this quirky format in the past decade. As with the Extended ATX products, they have no clear advantage over their smaller ATX cousins, other than more memory DIMMs (up to 8) for building powerful workstations. With that said, XL-ATX motherboards are slowly disappearing from the market, so it’s pretty unlikely that you’re going to run into this format anytime soon.

 XL-ATX Motherboard
XL-ATX Motherboard
  • Supports more memory
  • Very rare
  • Can’t fit in most cases
  • Expensive because of their obsolescence and small quantity

Micro ATX (mATX)

mATX boards have a square shape, measuring 244x244mm (9.6×9.6 inches). They typically have between 2-4 RAM DIMMs, which is great if you’re looking to have a powerful PC in a compact case, and have up to 4 expansion slots, allowing you to run dual-GPU systems in a handful of cases. IO-wise, you’re going to have enough to get by. Manufacturers also often include extra features like built-in WiFi with this type of card, so you won’t have to use one of your few expansion slots to have such a feature available.

In terms of build quality, you can find boards that are on par with high-end ATX boards for around the same price. While you lose some inputs and outputs, you gain a smaller form factor and you’ll have access to a whole new lineup of PC cases to build in. When building in a small form-factor case, it’s important to dedicate enough time to cable management for better airflow and invest in the right components for a cohesive, well-thought rig.

 Micro ATX (mATX) Motheboard
Micro ATX (mATX) Motherboard
  • Smaller than ATX while retaining most of the features
  • Ability to include in more compact cases
  • Inferior power-delivery, not suitable for high overclocks


Mini-ITX boards are 170x170mm (6.7×6.7 inches) and are the smallest type of board that can still run full-sized PC components. While the mATX could still function in most aspects like an ATX board, mini-ITX boards are more of a compromise.

You’ll find no more than two RAM DIMMs on the typical mini-ITX, with a single expansion slot. With no support for multi-GPU configurations and not enough power to run high-end processors, since most of them are powered using a 4-pin connector, limiting the type of hardware that you can run efficiently on such a motherboard. That being said, CPUs are more power-efficient than ever, so you can still find plenty of boards that will allow you to overclock, you’re just not going to reach very high values with the limited VRM and cooling options.

 Mini-ITX Mothberboard
Mini-ITX Motherboard
  • of cases
  • Very compact
  • Can still run a fully-fledged PC
  • Limited IO
  • Power delivery is not ideal for high-end components

What’s VRM and Why It’s A Critical Element for a Well-Built Motherboard

VRM stands for the voltage regulator module. It’s comprised of MOSFETs, chokes, and capacitors. Each of them impacts the way power is distributed from the motherboard to the other components. 

MOSFET stands for metal oxide semiconductor field-effect transistor. Pretty boring, but it’s essential in ensuring that your processor runs efficiently at a stable current. Much like the power supply converts alternating currents to direct the current, the MOSFETs also amplifies or switches the electronic signal to match a particular component’s needs. The chokes are inductors that are used to limit the passing DC to a certain frequency, further ensuring a stable voltage while powering your CPU. Transistors function in a similar way.

Whether you’re planning on buying a premium gaming motherboard or are looking to snatch a good price on a clean-looking, business-branded model, you should always purchase a product that has an intricate VRM. The more chokes, MOSFETs, and transistors, the better the performance and reliability. 

Lastly, make sure that your future motherboard has solid-state transistors. Fluid-based transistors can burst, throwing acid onto your components, damaging the circuits, and cutting off power to multiple sectors of the board. 

What Type of Board Do You Need

All in all, it all boils down to personal preference when it comes to motherboard sizes. If you’re working with limited space in your home or at the office, then a small form-factor PC is a great choice. A mini-ITX board can rock a potent CPU-GPU combo, allowing you to run demanding software with a compact build. While it’s easy to source components for a compact system, the building process is kind of a drag, and inexperienced PC builders will struggle to get good cable management, resulting in bad airflow and high temperatures during bigger workloads. Fan size is also limited, so this type of system will be louder.

If you’re not constricted by space, then I think that an ATX-based PC is the way to go. Most of the time you’ll get a better VRM, better cooling, and you’ll always get more features. You can use the expansion slots to further customize your build, and you can run powerful hardware at great temperatures. Cooling will never be an issue, with middle-tower and full-tower cases supporting air, hybrid, and water-cooled builds, and the entire building process is much more user-friendly.

Andrew is one of three co-founders of BGFG, the parent company of PC Guide. A keen gamer and PC enthusiast, Andrew dabbles in a bit of writing sometimes - when he gets the chance to!