Motherboard Form Factors Explained

When it comes to your computer, and picking components, one of the most important ones you need to pick is your motherboard. It’s where all the other components sit, and it is that “one guy that runs the entire show”. It connects everything else, allowing the rest of the components to communicate. As such, it’s a critical part of your build.

This being said, when you start looking into a new motherboard, things get very confusing, very quickly. Yes, you might take a look at a list of the best motherboard for both platforms and pick the one that works best for you. But even in that scenario, the question about motherboard form factors pops up pretty much instantly.

If ‘form factor’ sounds a bit too fancy for you, note that it’s just another way of saying size. Motherboards come in a few main sizes. Depending on the build you’re going for, picking the right size is crucial.

Why do motherboard form factors matter so much?

Well, there are a few reasons, but let’s start with the obvious one – actual physical size. If you’re in the market, you’ll find that there are a few different sizes when it comes to PC cases. Therefore, you get to the simple conclusion that you can’t fit a large motherboard in a small case. This is why your choice of motherboard size will greatly dictate your choice of case size, and vice versa, depending on which one is more important to you. Of course, you can always fit a smaller motherboard in a larger case, but not everyone wants a massive case.

Source: Wikipedia / Kozuch. CC BY 2.0

Then you have the other big problem. Smaller motherboard form factors have less room for things like M.2 slots, PCIe slots, and sometimes even DIMM RAM slots, too. How much of a problem that is, depends on your specific needs. But the smaller you go, the more you’ll be limited in this regard. This is why if unsure, it’s better to go for a larger motherboard.

On the other hand, some things are pretty much the same regardless of what form factor you go for. The first one is the CPU – this doesn’t depend on the form factor at all. Instead, it depends on the chipset and socket found on the motherboard. The second one is compatibility with graphics cards. So long as you have a PCIe x16 slot, you can put a graphics card in it. Well, provided it fits in your case, that is. And last but not least, you have the rear I/O, which doesn’t depend on the form factor at all. This is up to the manufacturer to decide what ports you get, and where they’re placed.

So, with that in mind, let’s take a look at the three most common motherboard form factors. Then, we’ll also discuss some others that you won’t come across as often.

The three most common motherboard form factors: ATX, micro ATX, Mini-ITX


ATX is pretty much what you’d call the “standard” form factor. It’s the size that fits in most mid-tower and full tower cases. It is also the one that offers a vast variety of features and plenty of expansion slots. The size for this form factor is usually up to 12 by 9.6 inches. This gives manufacturers plenty of room to add expansion slots.

What are some of the features you can expect to find on an ATX motherboard? Well, to begin with, they come with two to eight DIMM slots, but most commonly, you get four. This is just perfect if you want to go with two RAM sticks, to begin with, and then upgrade with two more down the road. These are usually DIMM slots, as opposed to the SODIMM slots you find on laptops and some smaller motherboards.

Then, you’ve got the expansion slots. With an ATX motherboard, you’ll oftentimes find multiple PCIe slots. This is also where you’ll commonly get support for multi-GPU setups. But multi-GPU setups aren’t as cool as they once were, so that might not be that much of a game-changer. On the other hand, those slots can be used for high-speed expansion cards like Thunderbolt cards, or high-end audio cards.

Next up, you have room for storage. While even the most compact motherboards will give you multiple SATA ports, nowadays it’s all about fast NVMe drives, and for that, you need M.2 slots. Most motherboards will get you at least two of these. However, some higher-end models will go up to three M.2 slots, and add heatsinks to each one of them. This does depend on the specific motherboard, though, so keep that in mind.

When you’re building a new PC, it’s usually best to start looking at an ATX motherboard. If you’d like to go for a more compact case, see which slots and features (if any) you could sacrifice. Then, you’ll know whether or not a smaller form factor is a viable option for you.

Micro ATX

Micro ATX motherboards are actually quite a bit smaller than conventional ATX. However, they don’t sacrifice that much in regards to functionality and features. They come at 9.6 by 9.6 inches. This is why they’re a great choice for people looking to downsize a bit and get a smaller case. You still get a lot of the features of an ATX board. Oh, and they’re sometimes cheaper than ATX, too, because they initially came to market with that idea – be cheaper than ATX.

When it comes to DIMM slots, you can get two to four here, because there’s no physical room for more. Most manufacturers tend to have four, so you should be covered in case you want to get two now, and two later.

Expansion slots are one of the compromises you’ll have to make if you go micro ATX. Yes, you’ll oftentimes get two PCIe slots, sometimes even more. Hoever, don’t expect to get 6 or 7 – there’s just not enough room for that. You should still be covered when it comes to adding a GPU, and maybe one to two expansion slots.

Storage is the second compromise you’ll need to make. Very few micro ATX motherboards will get you more than a single M.2 slot. Yes, SATA is always an option, but as we mentioned – nobody gets SATA nowadays, it’s all NVMe.

If you’re going for a compact build, but you still want to keep most of the functionality and upgrade potential down the road, a micro ATX motherboard is a great middle-ground between the large ATX and the extremely small mini ITX.

Mini ITX

Mini ITX is where you start to notice significant cut downs in terms of expansion slots because you’re only looking at a 6.7 by 6.7-inch motherboard, so there isn’t all that much room to work with. But for people who want the absolute smallest case, or are building an HTPC that would sit in their living room, mini ITX builds are a great pick.

The most notable compromise you’ll be making is the DIMM slots – mini ITX motherboards only come with two of them. Now, if you want to upgrade down the line, you’ll either need to get a single stick (and miss out on dual channel) or get two sticks but sell them down the road to get higher capacity ones. None of that is ideal, so it’s best to get plenty of RAM from the get-go.

The second big compromise is storage because mini ITX motherboards only come with one M.2 slot. There are even some that are so small that the slot is actually on the back of the motherboard. Honestly, this isn’t an ideal solution. You do get a couple of SATA ports, though, so you can always expand with slightly slower storage.

In terms of PCIe slots, you only get one. You can use it for your GPU, or you can use it to get a PCIe riser card which gets you multiple slots. That, however depends on the case. If, for example, you’re building this into a multimedia HTPC, you don’t really need a GPU. Or, you can get a low-end one that’s enough to render 4K content, so this isn’t too much of a problem.

Honestly, we wouldn’t recommend a mini ITX motherboard unless you’re really limited in terms of space. They showed up to the market about 20 years ago as a niche product, and their prices are still pretty high for all the compromises you’ll have to make. So if you have room, go for at least a micro ATX board.

Some slightly less common motherboard form factors

The three form factors we just discussed are the most common ones, and the ones you’ll want to consider with a conventional PC build. There are some other form factors that you’ll also come across. These were primarily made to fill the needs of a niche market, but if you have specific requirements that you can’t fulfill with a conventional motherboard, they may be a good pick for you.


eATX basically stands for extended ATX, which is a larger ATX motherboard. The dimensions here are 12 by 13 inches, and one of the most notable advantages, at least with some of these motherboards, is the dual-socket support. You can have two CPUs in this kind of motherboard, which is especially useful for servers.

The other big thing is that some eATX motherboards also give you four more DIMM slots for a total of eight. And that’s not all, but in some situations, you will also get quad-channel memory. However, this is oftentimes reserved for the most high-end models, and will cost you quite a lot.

LPX and mini LPX

LPX and mini LPX aren’t too much of a standard in terms of motherboard form factors. Instead, they’re built to fill in the niche that is low profile cases. They come with a pretty specific layout and oftentimes only support SODIMM memory in order to keep the profile as low as possible.

These kinds of motherboards you won’t come across too often, because they’re made to fit in prebuilt, low profile cases. Due to this, the cooling performance is pretty poor, and you have very little options in terms of upgrades.

Which one is right for you?

This is a question most of us would like to answer, but unfortunately, the answer isn’t that simple. So, how do you figure this out?

First up, make sure you have an overview of your components. Check how many SSDs you’re using, whether or not you also have mechanical drives, and see how many RAM sticks you’ll be going for. While we’re at it, consider whether or not you will be potentially upgrading RAM down the line, too. Then, see whether you’re going to use a discrete GPU, and whether or not you have other expansion cards that could take up a PCIe slot.

Once you have an idea of just how many slots you’ll need, you can take a look at what form factors fit you best. Chances are you’ll end up with either a micro ATX or an ATX board unless you’re building an HTPC.

Then, it’s a matter of figuring out what kind of case you’d like. If you can pick and choose between ATX and micro ATX, you could also downsize your case. That is provided your GPU fits a smaller case, and you don’t have too many components that you otherwise wouldn’t be able to fit.

At the end of the day, just like with pretty much any PC component, it’s a matter of being realistic about your needs, and getting the motherboard that can fulfill them, and give you a bit of room for upgrades down the road. Then, just consider your budget, and get the one that fits everything best!

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