If you’re interested in building a PC, one of the hurdles you have to overcome is deciding what motherboard to put in your PC; not only that, but you also have to opt for a size. Motherboards are probably the most important part of your system, as they facilitate all the communication and power delivery between components, which makes them pretty invaluable if you ask us. But what size is best?

Motherboard sizes are known as Form Factor, which have been standardized for a while. You might be familiar with the term “ATX,” which seems to be the most popular. Intel first coined the term in 1995; since then, it has been the de facto standard for PCs. Because of this standardization, users can pretty much freely combine whatever case and motherboard they want, and be relatively certain they’ll both fit together. Standardization is a beautiful thing.

Remember, though, you can’t just mishmash EVERY component without consequence; you need a CPU that matches the same socket as your motherboard, memory that fits your motherboard’s memory standard, and a GPU that won’t cause a system bottleneck. With that said, what is the difference between all of the form factors? Is there any specific advantage to one over the other? There are a few form factors to choose from that all have specific advantages. So, let’s explore.

Motherboard form factor overview

Here is a brief overview of the standard sizes of motherboards you can come to expect when building a PC We’ve outlined them in a nifty little chart for you to study. If you need a one-stop shop to understand motherboard form factors, then here it is.

These are the four main motherboard form factors that are produced today. Obviously, they come in a wide range of different chips, sockets, and memory standards, but that’s a topic for another article. Now we’ll go a little more into what features these different sizes usually carry and what use case they are best for. You might know the size you want, but will that motherboard have the features needed to fulfill your specific use case?

ATX

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 in all sorts of systems. Usually featuring four memory DIMMs, it can support dual or quad-channel memory, providing the user with better performance in specific applications compared to a board that doesn't support this type of configuration.

ATX boards usually have more than one expansion slot, allowing you to run multiple PCIe devices at the same time, if your case and power supply are up to the task. The number of expansion slots allows users to install quality-of-life upgrades, like a better network card or a storage card, for example.

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

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. You can provide the excess power by plugging in the additional CPU connector. P

Extended ATX (EATX)

Extended ATX boards (EATX) can support both mainstream desktop and workstation processors and are slightly bigger than ATX boards. These motherboards measure 305x330mm (12 x 13 inches rather than 12 x 9.6), giving you more PCIe connectors, especially on the workstation variants.

This is thanks to the additional PCIe lanes that workstation processors provide over desktop processors. They sometimes have dual-socket support, allowing you to run two CPUs using the same board, but this configuration is old now, and there are not many newer examples of this with current generations.

You can usually tell it’s a workstation configuration (by the chipset, usually) or take a look at the number of memory DIMM slots that the motherboard supports. Most modern workstation CPUs want more than the standard 4 DIMM slots.

Some EATX motherboards include built-in water cooling CPU blocks on standard desktop configurations because the extra space allows for them. These motherboards run you a lot of money, but they are designed to facilitate the most power and performance possible; cooling is a big part of that.

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 with expansion cards should you need them.

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. You can still get 4 Memory slots on a micro-ATX motherboard. Though some can have 2.

In terms of features, you’re not going to find as many as on a standard ATX form factor. This is because they are much smaller, for many reasons. Power delivery can often be an afterthought on these motherboards, even the high-end chipset variants, again because of the lack of space. But they still deliver in terms of performance.

This form factor can be fantastic when you’re looking to build a smaller PC that doesn’t compromise on power. Or, when building something like a multi-media PC, you want to sit quietly in the corner and not take up much space.

Mini-ITX

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. These motherboards are set out to be as small as possible, not as feature-rich as possible. We’ve seen people make portable PCs out of motherboards this size.

Mini-ITX motherboards can feature any chipset, though the price range varies dramatically, as you might expect. Just because it’s small doesn’t mean it’s bad. A Mini-ITX motherboard can feature all the same technology as a full-sized ATX Z790 motherboard.

XL-ATX

Unlike the other featured motherboard sizes, XL-ATX boards do not abide by a standard height and width. XL-ATX boards are very rare but deserve an honorable mention because of the sustained popularity of the Core i9 Extreme processors. This form factor has a lot of similar features and markings of an EATX motherboard, just slightly larger to accommodate better heatsinks and dedicated power and reset buttons. Think of these as mostly more dressed-up and refined EATS motherboards. However, they aren’t really in production anymore.

What is a VRM?

You might have seen mention of VRMs in this article and power delivery, but what does that all mean? It’s complicated, but essentially, 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. It's essential to ensure that your processor runs efficiently at a stable current. Much like the power supply converts alternating currents to direct current, the MOSFETs also amplify or switch the electronic signal to match a particular component's needs. All you need to know really is that the more power stages and the more robust the delivery system, the better.

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. 

What motherboard size 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 still 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 we 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.

What is the size of a motherboard?

The standard sizing of motherboards does mean we have known dimensions for them. The thickness may vary between models due to the number of layers they use and the quality they provide. There are also some variations that might extend a bit longer, but for the most part, here’s what the main boards should come in at.

Are motherboards one-size-fits-all?

If you’re asking about the physical motherboard size, not all motherboards will fit in the same cases. If you have a full or mid-size tower, you’ll likely have no issue fitting a motherboard up to ATX size. Although E-ATX or XL-ATX might be compromised and not have the right standoffs or enough space to be fitted.

However, if you have a smaller case, say micro-ATX or even mini-ATX, you have to get specific motherboards for that instead. Those require smaller sizes, such as micro-ATX and mini-ATX motherboards. So in terms of sizing, it’s not a one-size-fits-all.

It’s the same regarding processor compatibility with the socket they use. Each motherboard doesn’t fit each CPU, and you have to pair up the right sockets for each of them.

What does ATX stand for?

ATX stands for Advanced Technology Extended and was patented by David Dent in 1995, who worked for Intel. It was a version to improve the available standards at the time, mainly IBM’s AT design, and a big change in the motherboard designs, cases, and the power supplies as well. Allowing for this standard provides for a much better environment that’s easier to build with.

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About the Author

Sebastian Kozlowski

With a fascination for technology and games, Seb is a tech writer with a focus on hardware, news, and deals. He is also a tester and reviewer for the site. Contact him @ [email protected]