Motherboard Sizes: Form factors from e-ATX to ITX

You have decided on one of the best gaming motherboards but are still wondering the designations ATX, µatx (also: micro-ATX or mATX), mini-ITX (ITX), and e-ATX mean? Especially for first-time builders, it is very important to know the difference between the individual motherboard sizes or form factors.

Motherboard sizes

That’s why in this guide, we’ll show you the main differences between all the major motherboard sizes so you can get a better idea of which motherboard form factor is best for you and your build.

Motherboard Sizes: ITX, micro-ATX, ATX, and e-ATX at a glance.

Motherboard sizes are referred to as form factors. This can be confusing if you don’t know what they mean. In this section, we’ll look at each motherboard size and the difference between each form factor.

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e-ATX motherboards

Let’s start with the largest form factor: e-ATX. If space, in this case, is not an issue, but maximum performance, features, and reliability are important, e-ATX is the right choice for you. This is because the highest quality capacitors and MOSFETS (semiconductors) are usually installed here.

The e stands for “Extended,” which means that these motherboards belong to the category “Extended Advanced Technology Extended” (what a name). With the common dimensions of 30.5 x 27 cm (sometimes up to 34 x 33 cm), this makes direct sense because these things take up a lot of space in the case.

Generally, e-ATX boards are used for high-performance workstations and servers, but also high-end gaming builds. They are just as long as ATX motherboards but around 2.5-8cm wider. This extra space is generally used for the following:

  • a second CPU (however, there are also some with only one CPU socket).
  • e-ATX motherboards usually have eight RAM slots
  • Space for up to eight PCIe slots (some use an older 64-bit PCI standard called PCI-X)

While you can usually use the same processors on an eATX as on an ATX motherboard, you can’t always use a PCI card in a PCI-X slot without seriously affecting system performance.

The I/O panel between ATX and eATX is identical. Many who build a system with an e-ATX motherboard opt for a big-tower case (so that there is enough space). However, many mid-tower cases can be modified to fit eATX motherboards, although it will probably be a tight fit, and cable management can be complex.

Beware of (older) motherboards with PCI-X slots.

Not really common, but still present on old boards. PCIe cards do not work in a PCI-X slot. Therefore, check exactly which slots the motherboard has to ensure compatibility.

ATX Motherboards

The most popular standard for gaming PCs is ATX, which stands for “Advanced Technology Extended.” Most ATX motherboards come with up to 4 PCI/e expansion slots (this varies from model to model – there are also some with up to 7). These are needed for graphics cards, sound cards, NVMe PCIe SSDs, and various peripherals. In addition, the most common models offer up to four RAM slots and are generally housed in midi-tower cases.

ATX motherboards offer sufficient space (30.5×24.4cm) for components as well as cooling and associated cases still fit nicely on (or under) the desk. This motherboard size may be limiting if you need more graphics power (for SLI/Crossfire), fancy cooling systems, or more memory for an enthusiast gaming build or CAD workstation.

Fortunately, full-tower cases also support ATX form factors, which would give you a lot more room for things like pumps, more fans, or anything else.

micro-ATX (µatx, mATX)

As you can see in the diagram above, mATX motherboards have the same width as standard ATX motherboards but are a few centimetres shorter (24.4x24cm). This length disadvantage means that with micro-ATX, you often only get 1-2 PCIeX16 slots.

This makes micro-ATX motherboards unsuitable for multi-GPU setups or for users who want to use several PCIe slots. However, you get everything else here that you get with ATX. Often, m-ATX boards are the best solution for gamers, especially since the ratio between features, space, and price is perfect here.

mini-ITX motherboards

If you need a very small and compact PC, you should look at the mini-ITX format. This motherboard size is mainly used for extremely compact systems where the entire computer needs to fit in a closet or bookshelf or needs to be very light and portable.

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Typical applications are home theatre PCs (HTPCs), where low power consumption means less noise, or LAN PCs that need easy transport. Many new CPUs have integrated graphics chips, so you don’t even need a dedicated graphics card if you’re not aiming for high resolution or high frame rates.

Especially since the Mini-ITX standard only allows for one PCI expansion slot, CPUs with integrated graphics units are also a very practical solution for this. To take full advantage of the smaller form factor, you often have to look for something other than a standard ATX power supply, as these are generally too big for small Mini-ITX cases.

You are also limited in your RAM capacity, as mini-ITX motherboards only have two slots.

Few relevant sizes

There are other standards for PC motherboards that are even larger (XL-ATX) and smaller (pico-ITX and nano-ITX), but these are much rarer than the ones described above (and also less useful).

For most applications, ATX or mATX will provide the performance and features you need. Meaning, if you’re looking for a new motherboard these days, you’ll most likely come across one of the above sizes.

Advantages and disadvantages of motherboard sizes

Why would I want anything other than a standard ATX motherboard and case? Isn’t bigger better?

The answer to this is that there is an optimal application for each motherboard form factor for different scenarios.

This section we will explain the pros and cons of each form factor, so you have a better idea of which one best suits your needs.





  • Enthusiast overclocking

    Most PCIe slots

    Highest RAM capacity

    Ideal for 4x GPU builds, servers and high-end workstations

    Often the best capacitors & MOSFETS

  • Extremely expensive

    Requires a lot of space and a large housing

Standard ATX

  • Excellent overclocking potential

    Easy to find compatible components

    Often the best optics

  • Expensive

    Requires enough space


  • Often very cheap

    Space-saving & more mobile

    Small enough for "on the desk" builds

    Decent overclocking

  • Sometimes less RAM capacity than ATX

    Often fewer PCIe slots than ATX

    Not ideal for extreme overclocking

    Not suitable for multi-GPU


  • Very space-saving & compact

    Ideal for portable HT PCs

  • Only 2 RAM slots

    Only 1x PCIe

    ·   Often quite expensive

    ·   Limited when overclocking

    Very limited in GPU and cooler size

As you can see from the table above, all motherboard sizes have advantages and disadvantages that are relevant to a particular area.

  • Mini-ITX is only suitable for small PC builds and is not the first choice if you want to build something more powerful or versatile.
  • Micro-ATX is clearly the best all-rounder, as these boards are both smaller than ATX and have decent RAM capacity and PCIe slots.
  • ATX is top for those who want to build a PC that can handle any scenario, including multitasking and mining tasks.
  • e-ATX is the absolute giant baby for extreme use cases (not relevant for most of you).

Smaller does not mean slower.

To dispel this myth: Small mini-ITX boards are not slower than their bigger brothers. In fact, some of them are even faster in certain benchmarks. However, really good mITX boards are very expensive.

Which motherboard size should I choose?

If you’ve looked at the pros and cons over here, you probably already have some idea about which form factor is best for you.

However, if you’re still not sure, we’ll outline some common use cases here.

1. You want to build a cheap gaming PC

If you don’t have much of a budget, it’s best to get a Micro-ATX motherboard. The reason for this is that no component affects in-game performance as much as your graphics card, processor, and RAM.

The general rule of thumb when building a cheap gaming PC is, therefore, to allocate as much budget as possible to these three components. As a result, you’ll have to sacrifice some budget for your other components (which doesn’t mean buying low-quality components).

Fortunately, mATX motherboards are perfect for budget gaming PCs, as they still offer all the main features of standard ATX motherboards. The only real difference is that standard ATX usually provides better aesthetics, more PCIe slots, and better VRMs for overclocking.

2. You want to build a high-end gaming PC

Whether you want to build a high-end gaming PC with multiple graphics cards, overclock your CPU and push it to the max, or have a fancy motherboard as part of an excellent color scheme, the ATX form factor is the first choice for this.

While standard ATX motherboards already offer more than enough features, in some extreme scenarios, some of you will only be happy with an e-ATX motherboard. However, an e-ATX only makes sense if you have something very special in mind for the system.

3. You want to build a very small PC.

If you want to build a PC with a smaller footprint (for a very mobile computer or minimalist design), it is best to use a smaller Mini-ITX or Micro-ATX motherboard.

And of course, mini-ITX motherboards are the best choice if you want everything as small as possible. Perfect for LAN PCs or for HTPC systems.

Micro-ATX: The best all-rounder

Regardless of the application: we recommend Micro-ATX. The only scenario in which Micro-ATX would not be the first choice will be if you want a large number of PCIe outputs (for example, multiple GPUs for mining). Also, if you’re going to overclock heavily or just want something that adds to the overall aesthetic of the build, you will probably turn to ATX.

Conclusion: Choose the motherboard size for your needs

Hopefully, you now have a better understanding of motherboard sizes and form factors and can decide exactly what you need. If you’re looking for specific motherboard recommendations, be sure to read the articles linked below.

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