Motherboard Sizes: Comparing ATX, Micro-ATX, and Mini-ITX Form Factors (2022)

In this article, we will explore everything there is to know about motherboard form factors, from looking at the reasons why the particular sizes emerged to what are their assets and liabilities. We will also compare popular motherboard form factors of today, i.e. ATX, M-ATX, and M-ITX boards, to see which one you should buy and for which particular build.

History of Computer Motherboard

The IBM Personal Computer (1981) featured the first motherboard as we know it. At first, this component was called a planar, and at the beginning of its creation, went through several additional names until it was finally called the motherboard. This was the first time in computer history that a board housed the computer’s CPU and RAM, and provided audio as well as many other functions. This board also supplied ports for the keyboard and cassette tape and had expansion slots for add-on cards. There was even a system known as the bus to manage the information flow here. It was a revolutionary machine that changed the future of computing.
However, it was only in 1984, with the coming of IBM’s AT (advanced technology) motherboards that component-based PCs that we know today emerged. The AT form factor proved to be hugely popular and became the go-to form factor among PC manufacturers for several years. Though, this board did have its issues. One of the major problems with the IBM AT board was its enormous width (aside from limiting its use in smaller cases), and this made the board overlap with the drive bay designs of PC cases at the time. This essentially made the installation, troubleshooting, and upgrading of hardware a very tedious process.
To counter this problem, a smaller version of the original AT motherboard called the “baby AT“ was introduced back in 1987. The primary difference between these two variants was the width — the older full AT board was 12-inches wide, while the new baby AT was 8.5-inches in width. The design change made the IBM Baby AT motherboard way more compatible with PC cases of the time, and this led to its widespread adoption. The Baby AT was also the first PC motherboard to include sockets for I/O ports like serial and parallel. Both the AT and Baby AT sizes were widely used in 386, 486, and early Intel Pentium PCs and were the most widely used motherboards at the time. This doesn’t mean that there were no other competitors in the motherboard space at the time.
LPX (Low Profile eXtension) was a competing motherboard form factor developed by Western Digital in 1987, and it was used in the late 1980s and throughout the 1990s. An LPX motherboard was 9-inch x 13-inch in size, used a riser card, and had different placement of the video, parallel, serial, and PS/2 ports compared to other motherboards. The LPX motherboard never could match the stratospheric success of the Baby AT form factor, but it did remain a viable alternative throughout the early 1990s.

What Are the Different Sizes of Motherboards?

The 1980s and the early 1990s were a fascinating time for motherboard design, as every few years, a new standard would come, be used by a few manufacturers, and then ultimately die out. The process worked almost like clockwork, as this period saw the release of Intel’s Baby AT (1985), Western digital’s LPX (1987) platform, and even IBM’s NLX (1997) form factor.
But when it comes to motherboard form factors today, the situation is much more comprehensible. The vast majority of today’s consumer motherboards come in one of three sizes — ATX, Micro-ATX, and Mini-ITX. The ATX platform is currently the most popular of them all and has been the industry standard for a while now. It offers a ton of flexibility when it comes to expansion and upgradation, which makes this form factor the preferred one for gamers and PC enthusiasts. Mini-ITX, on the other hand, is the smallest of the bunch and is usually used in smaller PC builds because of its compact nature. The Micro-ATX motherboard form factor splits the two in the middle and gives us some flexibility when it comes to PCI-e and RAM expansion while keeping the overall size smaller than full-ATX. Furthermore, one might also come across an E-ATX motherboard, which is larger than a full-ATX board, but those are primarily used in workstation systems. Few other form factors do still exist like the Mini-STX, but they are fairly rare, and one hardly ever comes across them in build guides or retail stores.

Full-Size ATX Motherboard

The form factor which replaced the popular Baby AT standard and defined what the motherboard would look like for the next few decades was the ATX motherboard size. Developed by Intel in 1995, the ATX form factor was designed to address the many problematic areas that plagued the earlier boards.
ATX motherboard was created to enhance ease of use, bring better I/O support, and made available at a much lower price point. In terms of design philosophy, it is basically a Baby AT rotated 90 degrees. This change in design allowed the processor to be relocated away from the expansion slots, which gave it better airflow and made upgrading the PCIe card easier.
In terms of dimension, a full-size ATX board has a height of 305 mm (12 inches) and a width of 244mm (9.7 inches). The larger dimension is the major strong point of the board, as it provides manufacturers with enough space to install bigger heatsinks, intricate VRM solutions, larger rear-I/O, and more expansion slots. A full-size ATX motherboard, for example, typically has 7 PCIe expansion slots, allowing you to install up to 4 GPUs if your power supply can support such a configuration that is.
However, there are some drawbacks to the full-ATX form factor. One is that because it’s a large motherboard, it’s not compatible with all PC cases. Therefore, it requires one to research a bit more about the dimensions of their PC case before purchasing this kind of board. So, if you are thinking about upgrading to an ATX motherboard and have any doubts about the compatibility, do check your motherboard specs to see if the size is supported. There is also the issue of “heat” with ATX motherboards. The ATX’s component arrangement hinders airflow and many manufacturers claimed that this resulted in less than optimum cooling. The issue of heat was so severe that Intel released a new BTX motherboard series in 2005, which was supposed to fix the heat issues and supposedly replace the ATX form factor.
The BTX form factor introduced changes like moving the CPU socket toward the front intake fans. The idea was that fresh air intake from the front would remove excess heat as soon as possible, solving the biggest issue with ATX. It also tried to remove older standards like the PS/2 and parallel ports, replacing them with extra USB ports. In theory, it was a remarkable improvement over the decade-old ATX board design.
But as history would have it, the BTX form factor never reached the popularity that it was meant to achieve. Several reasons like sunk cost, community approval, and widespread adoption of ATX motherboard made both manufacturers and consumers vary of the new platform.
Another major benefit of the ATX motherboard size is upgradability. The expansion capability makes the ATX motherboard a perfect form factor for PC users who want to ensure they will never be caught in an inconvenient situation due to a lack of space or performance like hardcore gamers and other heavy users. But this emphasis on performance does not mean that an ATX board has no use for a regular user.
The very fact that the motherboard has sufficient space for additional memory, storage, and PCIe cards makes it future-proof for all kinds of users. It gives one the peace of mind that when new components get released, the ATX motherboard will always have a place for it.

Micro-ATX (M-ATX) Motherboard

Micro-ATX motherboards, as the name suggests, are smaller than full-size ATX motherboards. They were first introduced in 1997 and, according to Intel, were seen as a natural evolution of the ATX form factor. Computer sizes were reducing rapidly and manufacturers at the time believed that a smaller form-factor motherboard was essential for a future where mini-PCs would be the norm.
The Micro-ATX motherboard was also designed while keeping in mind a variety of users. For one, it was made to fill the gap that existed in motherboard form factors in the late 1990s. While most users used ATX at the time, users who wanted a small form factor had to sacrifice a lot in terms of capability if they went with a smaller motherboard. Micro-ATX solved this by giving users most of the capabilities of the full-size ATX board, while at the same time, keeping the form factor palatable enough to fit in smaller cases.
Dimension-wise, the micro-ATX motherboard is only slightly smaller than ATX with an overall surface area of 9.6 x 9.6 inches (244mm). This makes the board 25% percent shorter in length. To achieve this size, there are some features that the motherboard designer had to sacrifice. M-ATX boards have a maximum of 4 PCIe slots compared to a maximum of 7 on an ATX board, of which usually only two are x16 slots.
Perhaps the biggest benefit of M-ATX motherboard PCs, though, is cost. Thanks to their smaller size and the materials that go into making the motherboard, you can see a noticeable saving by opting for an M-ATX over a full-size ATX motherboard. So, if you want a PC that does not dominate your desk in the way that a full-size tower does, or need to make the most of a smaller space and take full advantage of your budget, then a Micro-ATX motherboard size might be the best choice for you. PROSCONSSmaller form factor while having most featuresLack of expansion slotsAbility to fit in more compact casesInferior power deliveryCheaper than other boardsI/O ports can be limited

Mini-ITX (M-ITX) Motherboard

If the M-ATX platform is still big for you, and you are looking to build an even smaller but capable PC, there is another motherboard size worth considering — Mini-ITX. An acronym for Information Technology extended, ITX is a small motherboard form factor developed by VIA Technologies, which was first introduced in November 2001 with the Mini-ITX platform. Many other versions of the ITX motherboard design, like the Nano-ITX in 2003 and the Pico-ITX in April 2007, have since been released. However, it’s the Mini-ITX form factor that has remained the most popular of the bunch, especially for desktop users.
ITX motherboards are popular because of their compact design and are often used in low-cost setups in cars, network devices, set-top boxes, and other small computers. They are seen as small, reliable platforms that can power relatively weaker PCs rather effectively. But Mini-ITX boards, for reasons that only computer enthusiasts know, have taken a different path as compared to their initial use cases. It is now employed by the PC building community and large manufacturers as a platform for building compact high-performance PCs, which are no bigger than your average game console.
In terms of dimensions, the Mini-ITX board is squarish in its design philosophy as it’s only 6.7 inches in both length and width (6.7 × 6.7 inches) This makes Mini-ITX the smallest type of motherboard that can still run full-sized PC components out of the box. So what are the compromises here?
While the M-ATX board could still function in most aspects like an ATX board (Rear I/O, memory slots), the Mini-ITX board size is more of a compromise. For one, M-ITX boards typically only feature a single PCIe lane. This limitation means there is no support for multi-GPU configurations or other expansion cards. You will also not find no more than 2 RAM slots on the typical mini-ITX motherboard, which decreases the total amount of memory you can have in your system compared to an M-ATX board (4 slots).
Furthermore, because of lack of physical space, M-ITX boards tend to have fewer VRMs than, let’s say, full-size ATX boards. This sort of limits the overclocking capability of the chips as power delivery is compromised in comparison to a larger board. Cramming a lot of components onto a smaller space may also create more heat dissipation problems. That said, CPUs have become more power-efficient over the years, so you can still find plenty of boards that will allow you to overclock. Though, you are just not going to reach very high clock speeds with the limited VRM and cooling options in Mini-ITX boards. However, the advantage of Mini-ITX motherboards, as mentioned above, is their smaller size. These boards are typically compatible with more small form-factor cases than both standard ATX and micro-ATX motherboard sizes. For example, a typical ATX mid-tower like the Corsair 4000D has a size of 453mm x 230mm x 466mm, approximately 48,552 cubic centimeters of space. A Mini-ITX case from Cooler Master like NR200, with room for a full-sized power supply and gaming-grade GPU, is 200mm x 320mm x 400mm, about 25,600 cubic centimeters. So you could stack 2 Mini-ITX cases together, and they still wouldn’t be as big as a standard mid-tower case. There are even smaller options, including Nano-ITX and Pico-ITX, but you won’t find many mainstream PCs in either of those form factors.
Finally, if we talk about the price, you would be surprised to know that these smaller Mini-ITX motherboards are more pricey than the Micro-ATX models and have quite a bit more features in them. Its high price, however, is a sort of premium that you pay for having a bespoke motherboard type. ProsConsCan fit in the most compact of PC casesI/O not comparable to other Motherboard standardsCapable enough to power a High-end gaming PCLimited VRM performanceMore expensive than M-ATX

While ATX, M-ATX, and Mini-ITX make up the majority of motherboards these days, it doesn’t mean there aren’t other options for people looking for specific workloads. In this section of the article, we will look at the other “less popular” motherboards you can still find on the market.

Extended-ATX (E-ATX) Motherboard

If you look for a slightly bigger motherboard than the ATX, there’s an extended version of such motherboards available as well. It is known as the E-ATX form factor, which basically stands for extended-ATX. The motherboard dimensions (12 x 13 inches) are slightly different from ATX, as it boasts the same length at 12 inches but is substantially wider at 13 inches.
The features and basic I/O ports of this motherboard category are similar to that of an ATX motherboard. But, since the size of the chassis is bigger, E-ATX motherboards generally have more expansion slots compared to ATX boards. For example, an ATX size board usually has 3-4 PCIe x16 slots, while E-ATX boards usually come with 4 or more slots. Similarly, ATX motherboards usually come with 4 RAM slots, whereas E-ATX has 6 and even sometimes 8 RAM slots. You can also expect an EATX motherboard to come with a few more additional heat sinks than ATX boards.
But the biggest difference between the two motherboards is the fact that E-ATX boards sometimes have support for dual-sockets, which allows you to run two processors at the same time. This is usually reserved for workstation-class hardware, but the fact that the board can accommodate up to 2 processors is impressive in its own right.

Mini-STX Motherboard

The next type of motherboard we will be looking at is the Mini-STX motherboard (Mini Socket Technology Extended), which was originally called Intel 5×5. Released in 2015, this motherboard measures 147mm by 140mm in size, which makes it 5.8 inches in length and 5.5 inches in width (not really living up to the 5×5 moniker). Unlike other small form factor boards like NUC or mini-ITX, which have a square shape, the Mini-STX board is 7mm longer from front to rear, making it slightly rectangular.
The basic rationale behind the 5×5 form factor was to provide PC builders with a motherboard with an upgradeable LGA socket that stayed under the ultra-compact volume benchmark of one liter. With Mini-STX, Intel’s intention was to create a platform that was much smaller than the dominant motherboard designs of the time but still had the hardware to pack a decent amount of performance.
However, as we have seen over the years, the platform has not picked up in terms of popularity. As of today, only one major manufacturer ASRock still produces a motherboard of this form factor, and even that hasn’t been updated for the newest Intel sockets. Furthermore, the proprietary Nvidia MXM GPU modules used with this motherboard have been discontinued. So, it’s fair to say that the mini-STX motherboard is dead in a sense and unless board partners like ASRock come up with something new (maybe an AMD partnership), the platform is unlikely to see a revival.

Which Motherboard Form Factor Should You Choose?

Now that we have given a detailed overview of the qualities and specifications of the different types of motherboards and their sizes, let’s look at which motherboard you should buy and for what use. As we have previously discussed, not all motherboards are created equal, as each one of them has its strengths and weaknesses.
For example, deciding which motherboard might be for you will heavily depend on what workflow you have or how many PCIe and RAM slots you will use. To make the answer of which motherboard you should buy easier, we have divided this section into three parts — best motherboard for a Budget PC build, best motherboard for a Gaming PC, and best motherboard for a Mini-PC.

For Budget PC Build

Choose a Micro-ATX motherboard sizedon’t splurge on a bigger motherboard and more component slots

If you want to go for a budget build, where a considerable sum of your total budget will go toward the processor and the graphics card, your best bet is to pick up a Micro-ATX motherboard. The reason is rather simple: there are no components that will have as much of an impact on your day-to-day performance as your processor and graphics card. These two components form the base for other PC components like storage and memory, and thus, you need a good CPU and GPU to even make full use of other PC parts.
So, if you are building a budget PC, remember to allocate as much as your budget to these two components. However, this does mean that you will have to sacrifice a bit on the quality of your other components or will have to give away in terms of features. But M-ATX motherboards come in handy for budget builds, as they can be anywhere from 30-40 percent cheaper than their full-size counterparts. And though they are cheap, they still have all the main features that ATX motherboards have. The only real difference is that full-size ATX boards can offer better thermals, as they can physically have more VRM and MOSFET modules and also that it can physically incorporate more PCIe slots.
These features, while important, are not that useful when it comes to budget builds. Budget CPUs don’t necessarily have the overclocking headroom required to fully make use of the more robust VRM solution of ATX boards. Furthermore, budget builds are typically single-card builds, as a second GPU might push the build over the budget limit.

For High-End Gaming PC Build

Always buy a full-size ATX motherboard for high-end gaming PCsOffers up to 7 PCIe slots, making upgradability a cinch

On the other end of the spectrum, high-end gaming PCs are far different from their budget counterparts. For a high-end gaming desktop, having multiple graphics or expansion cards is not uncommon. Moreover, in a quest for supreme performance, most high-end gaming PCs are also overclocked, which means that the motherboard needs to have a robust power delivery system to match these increased power requirements.
For this kind of build, the only suitable motherboard option is the full-size ATX motherboard. With up to 7 PCIe slots, the Full-ATX motherboard gives the user the option to not just have multiple GPUs but also gives them the flexibility to install other add-on cards like capture cards, PCIe SSDs, or even 10-gigabit network cards.

For Small Form-Factor PC Build

Buy a mini-ITX or micro-ATX motherboardConstraints on upgradability and part availability

If you want to build a PC with a smaller footprint, whether because you want it to be mobile or prefer a more minimalist design, your best bet is to go with a smaller mini-ITX or micro-ATX motherboard. If you want to save a little space and a little money, whilst still packing the most powerful of components into your new PC, M-ATX may be what’s best for you. Just be aware that you won’t have many options when it comes to picking your motherboard and case, and your cooling and storage may not be as expansive as they would be in a larger design.
But if you want the smallest build possible, without opting for a proprietary solution like an Intel NUC or a Corsair one, then blindly go for Mini-ITX motherboards and build yourself a portable gaming beast.

What PC Cases Are Compatible With My Motherboard?

The simple answer to this question is – it depends. Certain PC cases can fit all types of standard motherboards, but there are a few that do not. To understand this better, we should look at the different PC case sizes available in the market. If you are upgrading your PC case and don’t know which motherboard you’re using, read our detailed guide on how to check which motherboard you have on Windows right here.
There are essentially four common sizes for PC cases — Small Form Factor, Mini Tower, Mid Tower, and Full Tower. There are additional sizes, such as Ultra Tower and HTPC, but they serve a very specialized purpose and are generally not intended for a typical commercial home, office, or gaming PC.
Each of these case sizes has recommended motherboard sizes that they can accommodate. For example, a small form factor PC is the best use-case scenario for the Mini-ITX motherboard size that we discussed earlier. But this does not mean all cases are exclusive to a specific motherboard size. A mid-tower PC case, particularly intended for ATX motherboards, can fit smaller M-ATX and mini-ITX motherboard types as well. Recommended case sizes are just a kind of guideline, which tell you the best case (pun intended) scenario for the given motherboard, and are not to be read as gospel. So if you already have an M-ATX board and want to change your PC case, you should have a range of choices for new cases as you can use either small factor cases or even the larger Mid-tower cases.

Types of Motherboard Form Factors Explained

In the above article, we have rounded up not only the three mainstream motherboard sizes: ATX, Micro-ATX, and Mini-ITX, but we have also explored other less common options like E-ATX and the mini-STX. In the process, we also explored the long history of motherboard design and the variety of approaches that early motherboard manufacturers took to set themselves apart.
Now, why did we do that? We believe that before buying a motherboard, it is fundamental to understand the different form factors and their use cases. It helps you make a better decision. Having knowledge about the different types of motherboards will give a significant advantage to builders who want to create their PC for a specific purpose. So if you wish to build a gaming rig or a workstation, choosing the right motherboard type is crucial. That’s pretty much it. If you have further questions about how specific parts of the motherboard work, read our detailed overview linked here.