Motherboard Size Guide: EATX vs ATX vs mATX vs ITX

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Motherboards for both Intel and AMD processors are available in different sizes or form factors, which can be a bit confusing if you are new to PC building. The main motherboard sizes are EATX, ATX, micro-ATX, and mini-ITX. In this motherboard size guide, I go over all the different motherboard sizes and cover everything that you need to know about each.

Motherboard Size Comparison

As mentioned, there are four main motherboard sizes for consumers: EATX, ATX, mATX, and ITX. The following is a breakdown of the basic features of each motherboard size and a breakdown of each.

Max. Dimensions12 × 13 in
(305 × 330 mm)
12 × 9.6 in
(305 × 244 mm)
9.6 × 9.6 in
(244 × 244 mm)
6.7 x 6.7 in
(170 × 170 mm)
RAM Slot2 to 82 to 82 to 42
Expansion Slots4 to 8 PCIe4 to 7 PCIe2 to 4 PCIe1 PCIe

To give you an idea of how large (or small) these boards are relative to each other, here are a few typical models to scale.

Motherboard size comparison to scaleFrom left to right, the pictured motherboards are Asus ROG Maximus Z790 Extreme (EATX), MSI MAG X670E Tomahawk (ATX), ASRock B760M PG Riptide (mATX), and Gigabyte B650I Aorus Ultra (ITX). You will note that EATX and standard ATX boards have the same height, but EATX is wider and can vary in width up to the maximum of 13 inches. The mATX and ITX form factors, on the other hand, are always perfectly square.

In addition to these common form factors, there are at least a dozen other standards that are much less common, have been discontinued/superseded, or are aimed at workstations and servers.

Extended ATX (EATX)

Extended ATX or EATX is the largest motherboard form factor, and while it is very similar to ATX in terms of functionality, EATX motherboards are wider and have more PCIe expansion slots. These are typically used by enthusiasts or power users who need additional PCIe slots for multiple graphics cards or super-fast storage solutions.

Less commonly, some EATX motherboards have dual CPU sockets to accommodate two processors at the same time, and they can also have up to 8 RAM slots.

In any event, the substantial feature set means that not only are EATX motherboards larger, but also (much) more expensive. Since they occupy a niche market, they can also be harder to find in physical stores.


  • Ample expansion slots
  • Up to 8 RAM slots
  • Can have dual CPU sockets
  • Multiple GPU support


  • Larger and require EATX full tower cases
  • Premium pricing
  • Uncommon

Asus ROG Maximus Z790 EATX

The ASUS ROG Maximus Z790 Extreme is a typical example of an EATX motherboard. It supports the Intel 13th-generation CPUs and is noticeably larger than a traditional ATX motherboard. With the added size, it offers PCIe 5.0, DDR5 memory supports 24+1 power stages, five M.2 slots with PCIe 5.0, 10Gb, and 2.5Gb Lan, and dual Thunderbolt 4. It even comes with a Hyper M.2 card, which you can use to add even more M.2 storage.


The ATX motherboard form factor is the most common amongst gamers and general consumers since it offers a great mix of value, expansion, and features. ATX motherboards can fit inside ATX or mid-tower cases. They are smaller than EATX motherboards but bigger than mATX and ITX motherboards.

ATX motherboards typically have 4 RAM slots and 4 PCIe slots. These are available in different price ranges depending on the features and chipset. The ATX motherboard form factor provides ample expansion without being too big, and it is the go-to option for many.


  • Ample I/O
  • Decent expansion options
  • Offers a lot of functionality
  • Better VRM than some smaller boards
  • Multiple GPU support


  • More expansive than mATX

The MSI MAG B760 Tomahawk WiFi is a popular ATX motherboard that supports Intel 12th and 13th-generation CPUs. It has 4 RAM slots, supports DDR5 memory, and has three slots for M.2 SSDs. It even supports PCIe 5.0 for the graphics card. Other features include 2.5Gbps LAN, USB 3.2 Gen2, and Wi-Fi 6E. All in all, a very common feature set among mid-range ATX boards in 2023.

MSI MAG B760 Tomahawk WiFi

Micro ATX (mATX)

In recent years, ATX motherboards have started to get expensive, and mATX motherboards have emerged as the first choice for budget users. These are not as large as ATX motherboards and have fewer PCIe expansion slots, but they are still suitable for gamers and other users who have no need for overly extensive feature sets.

Despite the smaller form factor, most (but not all) mATX motherboards still feature 4 RAM slots and 2 full-size PCIe slots. The pricing of these motherboards can and do vary but mATX motherboards are typically cheaper than ATX motherboards. Both mATX and ATX motherboards can fit into ATX cases, but mATX motherboards can also fit into smaller mATX cases if you want to have a smaller build.


  • More economical than EATX and ATX motherboards
  • Compatible with ATX cases
  • Smaller form factor than ATX and EATX motherboards
  • Decent mix of features


  • Fewer PCIe expansion slots

The MSI MAG B660M Mortar MAX WiFi DDR4 is a great example of the budget-oriented nature of mATX. It supports DDR4 memory rather than DDR5, meaning that you don’t have to upgrade your RAM. It does not have PCIe 5.0, but it does have a pair of M.2 slots and supports Wi-Fi 6E.

MSI MAG B660M Mortar MAX WiFi DDR4



ITX or mini-ITX motherboards are for people who value size and want a smaller PC. This is the smallest of the common motherboard form factors with some built-in compromises. For example, ITX motherboards only ever have two RAM slots. This might not be an issue since high-capacity RAM is available, but it does mean that once the two slots are populated, you cannot add more RAM.

The smaller size can also mean restricted I/O and a single PCIe slot. This is enough for a graphics card, but you will not be able to install any additional PCIe parts. Not only are ITX motherboards compatible with ITX cases, but you can install them into larger cases as well.

You would imagine that a smaller motherboard would be cheaper, but that is where you would be wrong. ITX boards are typically priced higher than mATX and, in many cases, even ATX. You will need to pay a premium for a small form factor PC. It is also worth mentioning that since small form factor builds have less airflow, you might not want to pack very high-end components into a small ITX case. It goes without saying that this form factor is not ideal for overclocks or silent builds.


  • Ideal for compact builds
  • Provides all basic features


  • 2 RAM slots
  • Single PCIe slot
  • Limited I/O

A solid example in this category is the ASUS ROG Strix B760-I. It is both sophisticated and a bit pricey, with 8+1 power stages, supports DDR5 memory up to 7600 MT/s, PCIe 5.0, two M.2 slots, and USB-C.

ASUS ROG Strix B760-I

Which Motherboard Size Should You Pick?

The motherboard size that you pick depends on the kind of PC you are interested in building. If you value a smaller PC that takes up less space above all else, then ITX would be the best option. On the other hand, if you are on a budget and are looking for the most value for money, then a mATX motherboard would be ideal.

If you want to build a mid-tower PC with a lot of flexibility for future upgrades and expansion, then you should go with an ATX motherboard. I do not recommend an EATX motherboard unless you are interested in building a workstation that requires multiple graphics cards and storage devices. Most consumers and gamers will be more than fine with a mATX motherboard.

Factors To Consider When Buying A New Motherboard

Processor Socket

The processor or CPU socket is where you install the CPU on the motherboard. Making sure that the motherboard socket supports the CPU you have or are interested in buying is extremely important. Otherwise, the two parts are not going to work with one another.


Other than the CPU socket, the chipset of the motherboard can also be very important. Some features are exclusive to chipsets. Z series motherboards support overclocking for Intel K-series CPUs. In contrast, other chipsets do not have this feature. Z-series motherboards also support RAM overclocking and have 24 PCIe lanes. Chipset features and something that you need to consider when picking a motherboard.

AMD chipsets and CPUs are less locked down, as you will be able to overclock using the standard multiplier method even with the mainstream B550 and B650 chipsets and motherboards.

M.2 And SATA

NVMe SSDs are compact and very fast. Different motherboards have a different number of these. This is something that you need to consider when buying a motherboard. You should also consider the number of SATA ports a motherboard has if you have older SATA SSDs or HDDs that you want to use.


Wi-Fi can also be an important feature that you might want to get out of the box. This is not too important, though, since you can add Wi-Fi to any motherboard using an add-in card (AIC) or USB networking adapter.


The ports of the motherboard are another factor that you should consider when making a purchase. If you like to have multiple devices hooked up to your PC, then you might need numerous USB ports. Furthermore, you could have specific requirements such as USB Type-C or Thunderbolt.

This is what you need to know about motherboard sizes and what you should consider when buying a new motherboard in 2023. You can also check out our PC case sizes guide.

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