The motherboard form factor is a crucial specification that dictates thephysical dimension,mounting holes, andcase/power supply compatibility. It ensures all your hardware components are perfectly aligned with your needs.

Today, most manufacturers adhere to theATX standard, which has madePC buildingand upgrading a breeze for enthusiasts. However, non-standard or proprietary form factors also exist, which cater to unique user demands.

Most users go for the ATX standard. Amongst all, these are the most popular ones –full-size ATX, Micro-ATX, EATX, and Mini-ITX.

But don’t worry! I’m not going to limit this article to just these four motherboard sizes. For your comfort, I have categorized all the form factors into their respective families. This should help you better understand theiruse casesandcompatibility.

ATX Family

Let’s begin withAdvanced Technology eXtended(ATX). This is the most popular form factor in today’s date. Developed by Intel, there are a plethora of sizes, each catering to the needs of different users.

ATX hassuperseded the older designs(XT,AT,Baby-AT, andLPX) and has become the‘de facto standard’. But that doesn’t mean they are backward compatible with any of the mentioned form factors.

It has come with several revisions, the latest one being theATX 3.0. Each version has improved in terms of power delivery, spike handling, etc.

Whether you’re looking to build a powerful, enthusiastic, high-end, low-end, or even server system, this family integrates all types. Amongst all, these are the most popular variations –standard ATX,microATX,andExtended ATX.

Before we move on to the respective headings, here’s a summary of the most common types used today and how they differ.

Standard ATX

When someone refers to ATX, it usually indicates thestandard version. It has a rectangular design, measuring305 mm in length and 244 mm in width. The demonstration ofGIGABYTE B450AORUS ELITEbelow should give you a better insight into its size.

While this is the full-sized variant, even amini-sized versionwas introduced (284 mm × 208 mm). Unfortunately, it never became a standard and was completely removed starting from theATX 2.1specification.

you may directly plug the expansion cards into the several availableexpansion slots(maximum of 7as per the specifications). However, this completely depends on the manufacturer andchipset used.

Just understand that thefull-sized ATX boardshave a relatively large space enough to accommodateplenty of slots and ports. These usually include four DIMM slots, 6 to 8SATA ports, moreheaders/connectors, larger heatsink compatibility, and additional features.

Moreover, it consumes up to 70W of power andhigher-qualityVRM designs. So, this is a suitable choice for overclocking enthusiasts as well.

ATX boards do come with a few limitations. For instance, if you’re planning to install expansion cards, the PC case needs to have enough headroom. Clearly, it isn’t compatible with the small form factor cases.

Its component arrangement led tohigher heat generation, which is the reason Intel introducedBTX form factors.The latter was indeed better in terms of structural design and cooling. However, it could never replace the ATX form factor as planned.

Micro ATX

The full-sized ATX is already the best choice but it doesn’t satisfy the needs of those seekinglower-cost mid-end builds. Also, the Mini-ATX never met the demands, and a better solution was introduced –Micro ATX or mATX!

It follows the ATX principles but is relatively smaller in size. All boards are square-shaped with a physical dimension of244 mm x 244 mm. Check out myASUS PRIME B660M-K D4below to get a clear idea of what a microATX board looks like.

That said, these motherboards can easily fit intofull-towerandmid-tower cases(those ranging from 12 to 14 inches). Since it adheres to the ATX-standard location of the mounting holes, you shouldn’t face any issues.

It integrates a maximum of four I/O bus expansion slots. Plus utilizessmaller PSU form factors(not theATX but only SFX/TFX). You might expect a significant cost reduction, but even this depends on the manufacturer, chipset, and build quality.

Intel has even developed theFlex-ATX specification, whose size was almost 41% smaller than the full-sized ATX ((229 mm × 191mm). These boards came with a maximum of one expansion slot (in most cases, none). But, they were fully compatible with ATX or micro-ATX cases.

Extended ATX

The standard and micro versions of the ATX family are already popular. But this definitely wouldn’t suffice the needs ofservers and workstations.

Such users usually seek aquad-channel memory configuration, multiple graphics cards, and even dual processors! If you’re planning for a server system, it’s best to go for the eATX form factor. This happens to be thelargest and the most expensiveamong the three.

These motherboards can integrate eight DIMM slots, seven expansion slots, and more than eight SATA ports.

However, there isno official‘extended ATX’standard. So, the physical dimension completely differs based on themotherboard model. Most of these boards have a height identical to standard ATX boards and vary mainly on the widths.

But this isn’t always the case! Take a look at myGIGABYTE TRX40 AORUS MASTER.

This E-ATX board measures305 mm x 260 mm. Yours could be different. I highly recommend visiting your model’sTech Specspage to know the exact dimensions.

Well, motherboards adoptingSupermicro/ASUS’s eATX standardare usually305 mm × 330 mm. Despite that, none of the models share compatibleATX pattern screw holes. So, you need to be extra cautious whenpicking a casefor this build.

Other ATX Variations

Some manufacturers, like MSI, Gigabyte, Foxconn, EVGA, and Supermicro have come up with their ownproprietary or semi-proprietarystandards. These includeEE-ATX,Ultra ATX, andXL-ATX.

All of the aforementioned follow the ATX standard but their boards are comparatively larger. Also, they are mostly used inworkstation and server systems, like the EATX.

Let’s get into the basic specifications of all the other ATX variations that I have only briefly explained above.

ITX Family

While I’ve covered most form factors for desktops and server systems, what if you wish tobuild a smaller rig? Catering to these needs, theVIA Technologies Platform Solutions Divisionintroduced the ITX form factor.

Initially, this was proposed to supersede the Flex-ATX board. A design of215 mm × 191 mm(6% smaller) was proposed. However,a standard ITX version was never released.

Instead, VIA came up with themini-ITX design, which is also one of the most popular form factors today. It even rivals the ATX standard despite its small size.

Besides, thin Mini-ITX, Nano-ITX, and Pico-ITX are also abundantly used. Here are the general specifications before you proceed with the detailed explanation of each ITX motherboard.

Mini ITX

As the name suggests, this is a small form factor that comes with the minimum width and depth dimensions –170 mm × 170 mm. That’s almost 34% smaller than the Flex-ATX form factor.

Despite that, the I/O shield remains identical, with no feature reduction, whatsoever. So, even a small form factor cansometimes be better than the standard ATX motherboards. This completely depends on themotherboard chipsetthough.

For instance, myROG STRIX B550I-GAMINGmotherboard includes aUSB BIOS Flashbackfeature. But the other ASUS models (ATX ones) —ROG STRIX B450-F GAMINGorPRIME B450-PLUS, do not integrate such a feature.

From the above example, you might have noticed that Mini-ITX form factors are usually integrated with an‘I’in the chipset name.

To better manage space, these motherboards are usually equipped withless number of I/O ports,DIMM/expansion slots, andheaders. Thanks to its size, it can easily bemounted on any type of casing.

For better aesthetics, it’s always best to go for themini-ITX form factor, but don’t worry it can becompatible with NAS and other SFFs.

Usually,TFX PSUsare used to power these motherboards, and future upgrades are quite difficult.

Previously, only a few number of Mini-ITX boards were available, specifically from VIA. But today, you may find all popular motherboard manufacturers introduce different versions of the same motherboard model.

For example,ROG STRIX B450-F GAMINGandROG STRIX B450-I GAMINGboth use the same chipset. The difference is that the former is an ATX board while the latter belongs to the ITX family.

Thin Mini ITX

If you’re looking to buildthin-client PCs, opting for Thin Mini-ITX would be the best bet. However, such motherboards are quite rare to find. As per my intensive research, I’ve onlycome across ASUSandGigabyte offering this form factor.

There’s no subtle difference between the two in terms of dimension. But to adopt a thinner design, the number of I/O ports is reduced. Also, it usesSODIMM slots(just like in the laptop motherboard).

So, do all notebook computers use the Thin Mini ITX boards? Nope.

When it comes tolaptops, there’s no ‘standard’ form factor. This completelydepends on the modelused.

Other Small Form Factors

VIA has also introduced some more motherboard sizes in the form ofNano-ITX, Pico-ITX, Mobile-ITX, and Neo-ITX. They do not just differ in terms of dimension but also have specific use cases.

To cut it short, Nano-ITX is primarily used inmedia centersand set-top boxes. Their physical dimension is around120 × 120 mm.

Pico-ITX (100 × 72 mm) and Mobile-ITX (75 × 45 mm) are comparatively less used (only inembedded systems).

What about Mini PCs? Usually, they are sold as fully assembled systems and fall under the‘Nettop’motherboard type.

Check the demonstrated image ofGigabyte’s MZGLKAPabove. It has a dimension of112.6 x 119.4 mm, which neither falls under Nano-ITX nor Pico-ITX. But somewhere in between.

Likewise, there are other SFF motherboard types, likeCOM, USFF, UCFF, etc. A popular example of UCFF is theIntel Next Unit of Computing (NUC).

SSI CEB / MEB / EEB

These form factors were introduced by theServer System Infrastructure (SSI) Forumand are adopted by a handful of manufacturers.

I have come across a few boardsfrom Gigabyteand alsofrom ASUS. They are mainly used fordual-processor purposesin servers and workstations.

All three specifications arecompatible with the ATX familyand have identical mounting holes. However, they are larger in terms of width. Have a look at their basic specifications to understand how they differ:

Mini-STX

Only in the market since 2015, Mini-STX has been a popular choice for building small-factor computers. Currently, there are a handful of motherboards coming from ASRock with a standard dimension of140 mm x 147 mm.

Despite its small size, Mini-STX boards have a higher value withbetter performance. ASRock claims the motherboard can save14% on power consumptionafter thereplacement of a standard PSU with a DC-In Adapter.

Additionally, it offers better customization, at leasttwo M.2 slots,flexible LAN choice, aminimum of three video ports, etc. Thus, this can be an effective solution if you’re planning tobuild a budget and small-sized system.

Legacy and Proprietary Form Factors

Well, the motherboard types that I have discussed are just the ones that are popular in recent times. Turning back time, plenty of sizes were available that are now obsolete.

I still remember my first PC (Biostar MB-1333UCG). It was aBaby-AT form factorwith330 x 218 dimensions.

you may even findcrypto-mining-specific motherboardshaving a305 × 203 dimension. These have not just four or five GPU slots but integrate even up to 20!

Let’s not get into specific details or so. Here are some of the other motherboard types that are/were used. Even the below list is not complete as there are merely even more.

What Motherboard Form Factor Do I Need?

There’s nothing called the‘best’motherboard form factor. Each size serves a specific purpose and the choicecompletely depends on your needs and preference.

As I mentioned earlier, the four popular choices areATX, Micro ATX, EATX, and Mini-ITX. Go for the standard variant forgeneral-purpose office/home setup. But if you’re seeking to build a rig for yourserver or workstation, EATX would be the best.

For budget builds, I highly recommend Micro-ATX as they can be ideal for bothcompact and gaming purposes. The last one (Mini-ITX) is for those who seekportability.

Note that a small form factor doesn’t mean they are cheaper. In some cases, their price tag can go even higher than a full-sized ATX motherboard.

However,motherboard size isn’t the only thing to considerwhen getting a motherboard.CPU compatibility, chipset, future-proofing, warranty,aesthetics (usually that have RGB), and cooling are some other factors to keep in mind.