E-ATX vs. ATX vs. mATX vs. mini-ITX: Motherboard Sizes Explained

Whether you’re buying a prebuilt or custom PC, you’ll come across a relatively less-discussed specification. It’ll claim that the PC’s motherboard is “ATX” or “Micro ATX,” without really explaining what this means. Unfortunately, these motherboard sizes are very important to understand. While getting the wrong kind of motherboard won’t spell disaster for you, it could potentially hamper any future upgrades you have planned. This guide goes through E-ATX vs. ATX vs. mATX vs. mini-ITX motherboard sizes.

Good to know: motherboard VRMs are crucial! Find out what VRM is and how it affects CPU performance.

What Does ATX Mean?

These acronyms are referring to the “form factor” of the motherboard. Motherboards come in all shapes and sizes to fit an array of devices, from supercomputers to mobile phones. As such, there’s a need to differentiate all the different ways motherboards are made.

As you may expect, there are many form factors, each one designed to fit a specific role. You’re most likely to encounter one of four popular form factors when buying or building a PC: E-ATX, ATX, Micro ATX, and Mini ITX.

To start, let’s begin with the “standard-ATX” motherboard. ATX stands for “Advanced Technology eXtended” and was developed as far back as 1995. If you own, or have owned, a regular-sized PC, there’s a good chance it has an ATX motherboard. This makes ATX the “regular” choice when purchasing a PC or motherboard.

From ATX, motherboards get either bigger or smaller in size. Going bigger, you have the E-ATX motherboard (Extended ATX), which adds more area and components to the ATX board and is slightly larger as a result. Going the other way, you have the Micro ATX (mATX), which is smaller than ATX.

After that is the Mini ITX (“Information Technology eXtended”), which is even smaller than the Micro ATX. This may be confusing to some, as the “Micro” board is larger than the “Mini” one.

As far as size goes, we are listing these in order from biggest to smallest: E-ATX -> ATX -> Micro ATX -> Mini ITX.

Motherboard Sizes Comparison Chart

You may be surprised to know that there are at least eight commercially available motherboard sizes. Besides the four popular form factors we discussed above, there are four smaller sizes: Nano ITX, Pico ITX, 3.5″ Motherboard, and Femto ITX.

These smaller motherboards are usually single-board computers (SBCs) like the Raspberry Pi, which come with most of the PC components soldered onto the board itself.

But why do we have differently-sized motherboards in the first place? What advantages and disadvantages do the different sizes have?

Motherboard Form Factor Considerations

Case Size

For one, having a smaller motherboard allows you to have a smaller PC on the whole. Just like motherboard sizes, PC case sizes vary from Mini ITX to full towers. If you take a look inside a PC’s case, you’ll see that a lot of the height is taken up by the motherboard alone. If you want a smaller PC, it’s a good idea to start with a smaller motherboard.

Micro ATX and Mini ITX are choice picks for people who want smaller computers. Small PCs are great if you want something that’s portable or works as a server or media center that doesn’t take up much room. Just remember that components designed for ATX computers may not fit inside a smaller case.

Typically, a case designed for a specific form factor can also support smaller ones. For example, ATX cases are often designed so they can also hold Micro ATX and/or Mini ITX motherboards. Make sure you check the manufacturer’s specifications before buying a PC case that’s a different size than your motherboard.

Functionality

The smaller size does come at a cost, however. Smaller motherboards are made possible by removing components like expansion slots on the motherboard. The result is a motherboard that fits in smaller cases but doesn’t have the degree of upgradability that the larger form factors have.

The change from ATX to Micro ATX loses some of the PCI Express slots, which you need when installing a graphics card or SSD. Most ATX motherboards have around four PCI slots (usually 3x PCI-E x16 and 1x PCI-E x1, but this can vary between models), while Micro ATX has around three (2x PCI-E x16 and 1x PCI-E x1). This means less space for upgrades, such as graphics, sound, capture, and network cards. Mini ITX boards usually only have one PCI-E x16 slot.

Sometimes there will be a decrease in RAM slots and M.2 connectors as well. ATX to Micro ATX can go from four RAM slots and M.2 connectors down to two each. Mini ITX often has only two RAM slots, although some have managed four. USB ports can also take a hit as the result of a smaller board.

Of course, the opposite is true: The larger EATX boards will have more functionality. At the very least, they’ll usually sport four or more PCI-E x16 slots, which makes them a great choice if you have big plans for your PCI-E ports. In short, if you’re looking for a PC with many ports and upgradability options, stick with ATX or EATX over the smaller choices.

Some components demand even larger motherboards. The Threadripper CPUs from AMD, for example, require E-ATX motherboards (or sometimes even larger) with specific sockets to allow for all of the RAM slots and PCI-E slots that those CPUs can support.

Cost

While not always the case, Micro ATX motherboards tend to be the cheapest options. If you’re looking for a PC that you have no interest in upgrading or installing additional RAM or expansion cards into, you may be able to save yourself some money by opting for a smaller motherboard. Just make sure you don’t want to add too many components in the future. Otherwise, you may find yourself purchasing a larger motherboard down the line to fit your needs.

Are Smaller Motherboards “Slower”?

Despite the different motherboard sizes, you shouldn’t find that smaller motherboards “run slower” than larger ones. Of course, going smaller does mean you may sacrifice PCI-E and RAM slots, which will mean the PC’s potential power is less than its larger brethren. You may also find that smaller boards don’t handle overclocking as well as ATX and EATX boards can. They sometimes run hotter too. But, smaller motherboards don’t affect the performance of your PC simply due to being small.

Motherboard sizes can be confusing from performance and cost perspectives, but now you know their main differences, how they’re used, and which one will suit you the most. If you’re building a gaming PC, the best AMD gaming motherboards and the best Intel gaming motherboards will offer you fantastic options.

Tip: do you suspect that you have a faulty motherboard? Check out these warning signs of a bad motherboard.

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