Picking PC parts for a new rig? Fun times! But what’s not always so fun is figuring out the right motherboard size for your build. Choosing between Mini ITX vs. Micro ATX vs. ATX is a crucial decision because your motherboard dictates the rest of your build.
From expansion slots to SATA ports by way of price and dimensions, each form factor has its pros and cons. Sometimes the decision is made for you by specific requirements. However, if you’re stuck choosing between the three, this guide’s for you.
Mini ITX vs. Micro ATX vs. ATX : At A Glance
Before we start discussing the pros and cons of each motherboard size, let’s take a look at some key motherboard specs and see what each form factor offers.
|12 × 9.6 in
|9.6 × 9.6 in
|6.7 × 6.7 in
|Two or four
|PCIe x16 Slots
|One or two
|Six to eight
|Four to six
|Up to four
|Two to four
|Two to three
|One to two
There will always be exceptions for the number of slots and ports, but these numbers will apply to the vast majority of boards. In the next section, we take a closer look at the different features each form factor offers.
Mini ITX vs. Micro ATX vs. ATX: Features Compared
Size is the most apparent difference between the three motherboard form factors. If you’re building a portable PC or need to fit your rig into a compact cube case, this is the spec to pay close attention to. Depending on your case dimensions, you may be limited to Micro ATX (mATX) or even Mini ITX motherboards.
ATX motherboards are the largest of the three and will need to be installed in a mid or full tower case. The extra size has the benefit of offering more of everything. Whether it’s PCIe x16 slots, SATA ports, or M.2 slots, an ATX motherboard is undoubtedly the best option if you want room for expansion.
Micro ATX motherboards are as wide as ATX boards but lose a couple of inches in height. The shorter dimensions open up the option of more compact cases like the Corsair Crystal 280X RGB. These mATX cases offer some of the space-saving properties of a proper Mini ITX case without severe cooling and component compatibility sacrifices you get with the latter.
Mini ITX boards are perfect for small form factor (SFF) PCs and other situations where space is at an absolute premium. You lose out on PCIe slots and storage, but that isn’t a huge problem since SFF cases themselves won’t offer that much room for extra components beyond the essentials.
If you’re trying to choose between Mini ITX vs. Micro ATX for a compact build, consider how small your rig really needs to be. If you’re absolutely adamant on a sub-20 liter SFF PC, then ITX is your only option.
However, if you simply want something smaller and easier to move than a standard ATX tower case, mATX may be a better choice. You’ll be able to downsize your PC without needing to sacrifice as many features and expansion options as a Mini ITX motherboard.
ATX and mATX motherboards will offer the most RAM slots. Every mainstream ATX board will have four RAM slots, as will most mATX boards. There are mATX boards with two slots out there, but they’re not as common as they used to be. Mini ITX boards will only have two RAM slots; there simply isn’t enough space for more on such a compact layout.
We prefer having four RAM slots on our motherboard as it makes upgrades easier. The most common configuration for RAM kits is two 8 or 16 GB sticks. If you have one of these kits in a four-slot motherboard, upgrading memory is as simple as populating the empty slots with another kit.
On a Mini ITX motherboard with only two slots, you’ll have to replace your RAM outright, which is significantly more expensive. Sure, you can sell your old kit to recoup costs, but there’s no guarantee that you’ll be able to sell it quickly or at a high enough price.
Mini ITX boards currently max out at 64 GB of memory, while most ATX and mATX boards support 128 GB. Some ATX boards go even further with support for 256 GB of total RAM.
There’s no clear right or wrong choice here, but we certainly think four slots is ideal if you think you might want to quickly and cheaply add RAM in the future. The increased maximum RAM capacity you can get on an ATX board may be handy for heavy-duty workstation tasks too.
PCIe x16 Slots
With multi-GPU falling by the wayside, having multiple PCIe x16 slots for graphics cards isn’t as important as it used to be. But even if you’ll only ever run one GPU, extra PCIe slots can be handy for RAID cards, high-speed WiFi cards, or add-in PCIe SSDs like Western Digital’s AN1500.
However, it’s worth noting that rendering programs such as OctaneRender and V-Ray Next scale incredibly well with multiple GPUs. If you spend a lot of time in these programs and want to cut down rendering times, you may still want to consider purchasing an ATX board and loading it up with two or three GPUs.
Equipped with three slots, ATX motherboards are the best choice if you’d like to use multiple PCIe slots. As far as Mini ITX vs. Micro ATX goes, mATX is the safer choice between the two if you’re looking to keep your options open for additional cards in the future.
SATA and M.2 Slots
If you’re a storage fiend, an ATX motherboard is the way to go. With six or more SATA connectors and between two to four M.2 slots, you won’t be short of ways to connect hard drives and SSDs to your system.
Micro ATX boards don’t offer quite as many ports, but four to six SATA ports and two or three M.2 slots should be more than enough for most users. Mini ITX boards, of course, come out the worst here. You’ll be hard-pressed to find an ITX board with more than four SATA ports, and most only have one M.2 slot.
Some Mini ITX boards like the Gigabyte B550i Aorus Pro AX have two M.2 slots and are what we’d recommend if you’re building an SFF PC. The extra M.2 slot will likely come in handy since SFF cases will only hold so many 2.5 or 3.5-inch drives, and you’ll probably need the drive space for those mammoth 100 GB game installs.
M.2 SSDs essentially don’t take up any space in your system, so they’re a good way to get around limited drive bays. Just be warned that the second M.2 slot on a Mini ITX board will be on the backside, so make sure you populate that slot first when assembling your PC.
What’s The Right Size For You?
Now that we’ve discussed the primary differences between all three motherboard form factors, it’s time to look at the main reasons why you’d go with each particular size.
If you like keeping your options open for future expansion, ATX boards are the best choice. The abundance of PCIe, M.2, and SATA connections make for a board you can keep using for the long term even if your storage or peripheral needs expand.
ATX boards are also, of course, perfect if you already have many hard drives that need to be installed in your rig. Sure, you can buy PCIe-based SATA cards to add more ports, but that’s not as elegant or convenient as just having the SATA ports on your board to begin with.
A motherboard like the ASRock X570 Taichi with its eight SATA ports and three M.2 slots should offer enough storage expansion for even the most dedicated data hoarder.
High-end workstation users should also target ATX boards. The extra RAM capacity and PCIe slots are arguably essential for heavy-duty workstation tasks. Having large amounts of RAM is always handy, and an extra GPU or two can drastically accelerate rendering workloads.
Why Micro ATX?
Micro ATX is the safe mainstream option with everything most users will need without being too restrictive. Are you building a standard gaming rig with one GPU, a handful of drives, and no intention of expanding beyond that? In that case, an mATX board is probably the best choice.
Micro ATX motherboards are also often the most affordable options on the market. They have fewer ports and slots than ATX motherboards which helps reduce the cost. And they don’t require the planning and engineering that drive the prices of Mini ITX motherboards up.
An mATX board like ASRock’s B550M Steel Legend offers the same performance and important specs as its larger ATX brother at a lower price. The mATX board even has the same number of SATA ports, making the lack of a second PCIe x1 slot its only significant disadvantage.
We’d suggest anyone building a PC look at mATX motherboard options. Most of the time, you’ll find something that fits the bill without needing to spend much time evaluating other sizes.
Why Mini ITX?
The only reason to go with Mini ITX is size. These boards are designed specifically for HTPC and SFF computer builds, where compact dimensions are essential. You give up RAM slots, SATA ports, and extra PCIe x16 slots in exchange.
Keep in mind that small size doesn’t equate to a small price. MSI’s MPG B550I Gaming Edge Max WiFi actually costs more than the company’s ATX equivalent, the B550 Gaming Edge WiFi, despite having less of everything.
As far as the Mini ITX vs. Micro ATX decision is concerned, there are two ways to look at it. If features and ease of upgrades are on your mind, get the mATX board. But if you prioritize compactness above all else, Mini ITX is the only game in town.
Both will still be smaller than an ATX rig in a mid or full-tower, though, so it’s just a question of how small you want your rig to be.
Sizing Things Up
All in all, there’s no clear-cut winner in the motherboard size comparison. Micro ATX boards are the safest option, sure, but they might not always be the best for users with specific needs regarding components or case size. ATX boards offer more of everything, while Mini ITX motherboards are small enough to fit into neat space-saving cases.
Motherboard size, then, really will depend on what sort of user you are and what kind of rig you’re building. Determine what you need now and might need in the future; once you’ve figured that out, the choice should be straightforward. If you need more help identifying essential features to look for, head on over to our guide to choosing a motherboard.