Looking for a primer on the different motherboard form factors? In this post, we’ve highlighted the main differences between Mini-ITX, micro-ATX, ATX, and Extended ATX motherboards.
Should you get a micro-ATX, Mini-ITX, or standard ATX motherboard? What about an Extended ATX motherboard? And what exactly is the difference between all of these form factors?
If you’re looking to build a new computer, one of the most important components you’ll need to choose is a motherboard. However, motherboards can differ significantly in their size, features, expansion options, connectivity, and price.
Also Read: How to Choose A Motherboard
One of the things that first-time builders often struggle with is understanding the differences between motherboard form factors—or, more simply, motherboard sizes.
The motherboard’s form factor affects the type of case you can use, the number of expansion slots that can physically fit on the board, and, to some extent, how much room the manufacturer has for M.2 slots, connectors, heatsinks, and other onboard features.
However, motherboard size does not directly determine performance. A high-quality Mini-ITX or micro-ATX motherboard can perform just as well as a larger ATX motherboard when paired with the same components.
In this guide, we’ll break down the major motherboard form factors and explain which type makes the most sense for different kinds of PC builds.
Quick Motherboard Form-Factor Comparison
| Form Factor | Typical Dimensions | RAM Slots | Expansion Slots | Typical Use Case |
|---|---|---|---|---|
| ATX | 305 x 244mm | Typically 4 | Up to 7 positions | Gaming, Workstations, General Use |
| Micro-ATX | 244 x 244mm | Typically 2-4 | Up to 4 positions | Gaming, Budget & Compact Builds |
| Mini-ITX | 170 x 170mm | Typically 2 | 1 | Small Form-Factor PCs |
| E-ATX | Up to ~305 x 330mm* | Varies | Multiple | Enthusiast & Workstation Builds |
*Consumer E-ATX dimensions can vary between motherboard manufacturers. Always check the exact dimensions of the motherboard and the supported motherboard width of your case before buying.
Micro-ATX vs Mini-ITX vs ATX vs E-ATX: A Size Comparison
The most obvious difference between micro-ATX (mATX), Mini-ITX, standard ATX, and E-ATX motherboards is their physical size.
The standard dimensions for the three most common form factors are:
- Standard ATX: 305mm x 244mm (12.0″ x 9.6″)
- Micro-ATX: 244mm x 244mm (9.6″ x 9.6″)
- Mini-ITX: 170mm x 170mm (6.7″ x 6.7″)
Extended ATX: E-ATX is commonly associated with boards measuring up to approximately 305mm x 330mm (12.0″ x 13.0″). However, consumer E-ATX motherboard dimensions are not as consistent as ATX, micro-ATX, and Mini-ITX dimensions. Some E-ATX boards are considerably narrower than 330mm.
Because of this, you should check the exact dimensions listed by the motherboard manufacturer and compare them with the maximum motherboard size supported by your case.
As you can see in the image above, micro-ATX motherboards are about the same width as standard ATX motherboards, but they are shorter.
The additional PCB space available on an ATX motherboard gives manufacturers room to add more physical PCIe slots, M.2 slots, fan headers, storage connectors, onboard controls, and other features.
It’s important to distinguish PCIe slots from PCIe lanes, though. A larger motherboard does not automatically have more PCIe lanes. The number and configuration of available PCIe lanes are determined primarily by the CPU, chipset, and motherboard design.
For most gaming PCs, this distinction is less important than it once was because running multiple graphics cards for gaming is no longer a mainstream use case. Instead, the extra expansion space on ATX and E-ATX motherboards is more useful for devices such as capture cards, high-speed networking cards, sound cards, storage adapters, and other PCIe add-in cards.
Mini-ITX motherboards, on the other hand, are much smaller than both ATX and micro-ATX motherboards.
Mini-ITX boards typically have two memory slots and one full-length PCIe expansion slot. Despite their smaller size, modern Mini-ITX motherboards can still offer premium features such as PCIe 5.0 support, multiple M.2 slots, Wi-Fi 7, high-speed networking, USB4 or Thunderbolt connectivity, and capable power delivery depending on the specific motherboard.
Their primary advantage is that they can be installed in extremely compact cases.
Extended ATX motherboards provide even more PCB space than standard ATX motherboards. Manufacturers often use that additional room for larger VRM heatsinks, additional M.2 storage, more onboard controls, expanded connectivity, or other enthusiast-oriented features.
However, not every E-ATX motherboard provides more of everything. The exact feature set still depends on the individual motherboard.
Also Read: Which PC Case Size is Best for Your Next Build?
Ultimately, the most important impact motherboard size has on your build is determining which PC cases you can use.
For instance, if you want to build a small form-factor gaming computer, it is highly likely that you won’t be able to use a standard ATX motherboard. Depending on the case, you may not be able to use a micro-ATX motherboard, either.
On the other hand, larger ATX and full-tower cases commonly support smaller motherboards as well.
So, you can usually install a micro-ATX or Mini-ITX motherboard in an ATX case, provided the case includes the appropriate mounting locations.
From an aesthetics standpoint, though, you might not want to install a Mini-ITX motherboard in a large ATX case because the smaller board can leave a lot of unused space around it.
The opposite generally isn’t true. You typically cannot install ATX or micro-ATX motherboards inside Mini-ITX cases, and standard ATX motherboards will not fit inside cases designed exclusively for micro-ATX motherboards.
There is one additional compatibility consideration with newer motherboards: reverse-connector designs. Motherboards such as ASUS BTF, MSI Project Zero, and GIGABYTE Project Stealth models move many of the power and data connectors to the rear of the motherboard.
These boards still use familiar form factors such as ATX or micro-ATX, but they require a case with the appropriate openings behind the motherboard tray. So, motherboard size alone does not guarantee compatibility with a reverse-connector motherboard.
The Pros and Cons of Each Form-Factor
You might be thinking to yourself: “Why would I want anything other than a standard ATX or E-ATX motherboard and case? Isn’t bigger better?”
Not necessarily.
There is a time and place for each motherboard form factor. Your budget, case size, expansion requirements, storage needs, and preferred aesthetics should all play a role in your decision.
And, while larger boards generally have room for more connectors and expansion slots, motherboard quality varies significantly within every form factor.
In this section, we’ll go over the pros and cons of each option so you’ll have a better idea of which motherboard size makes the most sense for your build.
Extended ATX (E-ATX)
Pros
- More PCB space for expansion, storage, cooling, and onboard features
- Often used for premium enthusiast and workstation motherboards
- High-end models frequently offer robust power delivery and extensive connectivity
Cons
- More limited case compatibility than ATX, micro-ATX, or Mini-ITX
- E-ATX dimensions can vary, making case compatibility more complicated
- Premium E-ATX motherboards are usually expensive
- The extra features are unnecessary for most gaming PCs
Standard ATX (ATX)
Pros
- Excellent balance between size, features, expansion, and price
- Available with budget, mid-range, and high-end chipsets
- More room for PCIe slots, M.2 slots, headers, and other features than smaller boards
- Huge selection of compatible cases and motherboards
Cons
- Usually costs more than comparable budget-oriented micro-ATX options
- Requires a larger case than Mini-ITX and most micro-ATX builds
- Extra expansion slots may go unused in a typical gaming PC
Micro-ATX (mATX)
Pros
- Often offers the best value for budget and mid-range builds
- Smaller than ATX while still offering multiple expansion slots on many models
- Can support four DIMM slots and multiple M.2 drives
- Modern high-end micro-ATX motherboards are available with premium chipsets and features
Cons
- Fewer physical expansion slots than ATX
- Selection of premium models is smaller than it is for ATX
- Can look undersized inside a large ATX case
- There are fewer micro-ATX-focused case options than ATX or Mini-ITX options
Mini-ITX (ITX)
Pros
- Best mainstream motherboard form factor for extremely compact PCs
- Large selection of purpose-built small form-factor cases
- Premium Mini-ITX boards can offer high-end chipsets and features
- Ideal for portable gaming PCs and minimalist builds
Cons
- Typically costs more than similarly-equipped micro-ATX boards
- Limited to one PCIe expansion slot
- Usually limited to two DIMM slots
- Compact builds require more careful planning for cooling, GPU clearance, and cable management
- Small form-factor cases and SFX power supplies can carry a price premium
Which Motherboard Form-Factor Should You Choose?
If you’ve looked over the pros and cons of each motherboard form factor above, you probably already have a good idea of which option makes the most sense for you.
But if you’re still unsure, let’s go over a few common scenarios.
1. You want to build a budget-friendly gaming PC
If you want to build a budget-friendly gaming PC, your best bet will often be a micro-ATX motherboard.
The reason is simple: your graphics card and processor are going to have a much bigger impact on gaming performance than your motherboard’s physical size.
So, when you’re working with a limited budget, it usually makes sense to spend enough on the motherboard to get the socket, chipset, connectivity, storage support, and upgrade options you need—and then put as much of the remaining budget as possible toward components that directly affect performance.
Fortunately, micro-ATX motherboards are well-suited to this kind of build.
A good micro-ATX motherboard can still provide four memory slots, multiple M.2 slots, PCIe 4.0 or PCIe 5.0 support, Wi-Fi, 2.5Gb Ethernet, and more than enough connectivity for a typical gaming system.
And unlike in the past, choosing micro-ATX doesn’t necessarily mean settling for an entry-level chipset. Premium micro-ATX boards are available as well.
The biggest sacrifice compared to ATX is usually physical expansion space rather than gaming performance.
So, unless you know you need several PCIe add-in cards or a specific feature that is only available on a larger motherboard, micro-ATX is often one of the best ways to save money without sacrificing gaming performance.
2. You want to build a high-end gaming PC
If you’re looking to build a high-end gaming PC, a standard ATX motherboard will make the most sense for most users.
ATX gives motherboard manufacturers enough room to include multiple M.2 slots, larger heatsinks, additional PCIe slots, debug displays, onboard buttons, high-speed networking, additional USB connectivity, and robust power delivery without requiring an unusually large case.
If you want to overclock your processor, the quality of the motherboard’s VRM and cooling matters more than the form factor itself. However, manufacturers tend to offer their widest selection of premium motherboards in the ATX form factor.
E-ATX can also make sense for an extreme enthusiast or workstation-oriented build, especially if you need a particular flagship motherboard or additional onboard features.
However, you should not feel like you need an E-ATX motherboard simply because you’re buying a high-end CPU or graphics card. A quality ATX—and in some cases even a premium micro-ATX or Mini-ITX motherboard—can run a high-end gaming system without sacrificing performance.
3. You want to build a small form-factor PC
If you want to build a PC with a smaller footprint, whether because you want it to be easier to move, you have limited desk space, or you simply prefer a minimalist design, Mini-ITX and micro-ATX are your two main options.
If you want to go as small as reasonably possible with mainstream desktop components, Mini-ITX is generally the best choice.
Modern Mini-ITX motherboards can support powerful gaming hardware despite their compact dimensions. The biggest challenges usually come from the case rather than the motherboard itself.
Small cases can place restrictions on graphics card length and thickness, CPU cooler height, radiator size, power supply dimensions, airflow, and cable management.
You’ll therefore want to plan the entire system before purchasing any individual component.
Micro-ATX is another excellent option if you want something smaller than a traditional ATX tower without going all the way down to a tiny Mini-ITX build.
In fact, compact micro-ATX cases have become increasingly attractive because they can offer a noticeably smaller footprint while retaining more expansion options and using less expensive standard-sized components.
Small form-factor systems can be especially useful for gamers who regularly move their PC around, anyone with limited desk space, living-room gaming PCs, and minimalist setups.
Motherboard Form-Factor FAQ
Below is a list of frequently asked questions about motherboard form factors.
1. Can I install a Mini-ITX motherboard in an ATX or Micro-ATX case?
Yes, in most cases.
Mini-ITX motherboards use mounting locations that are compatible with larger ATX-based cases, so most ATX and micro-ATX cases that list Mini-ITX support can accommodate one.
However, always check the case’s official motherboard compatibility list before purchasing.
The biggest downside is primarily aesthetic. A Mini-ITX motherboard can look unusually small inside a large ATX case.
2. Can a Micro-ATX motherboard fit into a case designed for ATX motherboards?
Yes. Most ATX cases support micro-ATX motherboards because micro-ATX uses a compatible subset of the ATX mounting pattern.
Again, you should check the specific case’s compatibility list, but ATX cases commonly support ATX, micro-ATX, and Mini-ITX motherboards.
3. Is Micro-ATX suitable for gaming builds, or should I opt for ATX instead?
Micro-ATX is perfectly suitable for gaming builds, including many high-end gaming systems.
Motherboard form factor has very little direct impact on gaming performance. What matters more is the motherboard’s socket, chipset, VRM quality, memory support, BIOS, connectivity, and available expansion.
ATX is worth considering if you need more PCIe expansion slots, additional M.2 storage, more onboard connectors, or a particular premium motherboard that isn’t available in micro-ATX.
For most gaming PCs, though, a good micro-ATX motherboard can provide everything you need.
4. Do Mini-ITX motherboards offer the same performance as larger form factors?
They can.
The physical size of a motherboard doesn’t inherently make the CPU or graphics card perform faster or slower.
A quality Mini-ITX motherboard paired with the same processor, graphics card, and memory can deliver essentially the same gaming performance as an ATX system.
The important differences are expansion and system design.
Mini-ITX boards generally have only two DIMM slots, one PCIe expansion slot, fewer internal connectors, and less physical room for onboard components.
The compact cases commonly paired with Mini-ITX motherboards can also make CPU and GPU cooling more challenging.
That doesn’t mean Mini-ITX systems have to be slower, though. Modern premium Mini-ITX motherboards can have surprisingly robust power delivery and support high-end processors.
As long as the motherboard can properly power your CPU and the system has adequate cooling, choosing Mini-ITX does not automatically mean sacrificing performance.
5. What are the advantages and disadvantages of using a Mini-ITX motherboard?
The biggest advantage of Mini-ITX is that it allows you to build an extremely compact PC while still using mainstream desktop processors, graphics cards, and other components.
That makes Mini-ITX an excellent option for portable gaming PCs, minimalist desk setups, and systems where space is limited.
The tradeoff is reduced expansion.
Mini-ITX motherboards typically provide two RAM slots and one PCIe expansion slot. They can also have fewer fan headers, M.2 slots, SATA ports, and internal USB connections than larger motherboards.
Mini-ITX motherboards are also often more expensive than comparable micro-ATX models because manufacturers have to fit a large amount of functionality into a very small PCB.
6. How many RAM and PCIe slots are typically available on Micro-ATX and Mini-ITX motherboards?
Mini-ITX motherboards typically have two DIMM slots and one full-length PCIe expansion slot.
Micro-ATX motherboards usually have either two or four DIMM slots and can provide up to four rear expansion-slot positions, although the number and electrical configuration of actual PCIe slots varies by motherboard.
Keep in mind that the physical length of a PCIe slot doesn’t necessarily tell you how many PCIe lanes are wired to it. A slot that physically looks like a PCIe x16 slot may electrically operate at x8, x4, or another configuration depending on the motherboard.
7. Are Mini-ITX motherboards more expensive than Micro-ATX or ATX boards?
They often are.
Micro-ATX usually offers the lowest-cost options, while Mini-ITX motherboards frequently carry a premium because manufacturers have to fit power delivery, storage, networking, audio, and other components into a much smaller area.
Mini-ITX boards can therefore cost as much as—or sometimes more than—similarly-equipped ATX motherboards.
However, pricing varies significantly depending on the chipset and feature set, so it’s best to compare individual boards rather than assuming one form factor will always cost more.
8. Which motherboard form factor is best for building a compact or portable PC?
Mini-ITX is generally the best motherboard form factor if your goal is to build the smallest practical gaming or desktop PC.
It gives case manufacturers the most flexibility to create very compact enclosures.
However, micro-ATX shouldn’t be overlooked.
There are compact micro-ATX cases that are only moderately larger than Mini-ITX cases while offering additional expansion slots, four DIMM slots on many motherboards, greater component compatibility, and lower overall costs.
If absolute size is your priority, choose Mini-ITX. If you want a compact PC but still value expansion, easier cooling, and better value, micro-ATX may be the better option.
9. Is E-ATX a standardized motherboard size?
Not as strictly as ATX, micro-ATX, or Mini-ITX.
A size of approximately 305mm x 330mm (12 x 13 inches) is commonly associated with E-ATX, but consumer motherboard manufacturers also use the E-ATX label for boards with different widths.
This means that seeing “E-ATX support” on a case specification does not necessarily guarantee that every E-ATX motherboard will fit.
Before buying an E-ATX motherboard, compare the board’s exact dimensions with the maximum motherboard width supported by your case. You should also check whether a wider board will block cable-routing openings or interfere with other parts of the case.
10. Does a larger motherboard have more PCIe lanes?
Not necessarily.
The CPU and motherboard chipset determine how many PCIe lanes are available and how those lanes can be distributed.
A larger motherboard simply gives the manufacturer more physical space to install expansion slots and other components.
For example, an ATX board may have several full-length PCIe slots while a Mini-ITX motherboard has room for only one. However, that doesn’t mean every full-length slot on the ATX motherboard receives 16 PCIe lanes.
Always check the motherboard specifications if you plan to use multiple PCIe devices.
11. Do reverse-connector motherboards require a special case?
Usually, yes.
Reverse-connector motherboards move many power, fan, USB, and storage connections to the back of the motherboard. Examples include designs marketed under names such as ASUS BTF, MSI Project Zero, and GIGABYTE Project Stealth.
These motherboards can still use standard form factors such as ATX or micro-ATX, but the case needs cutouts behind the motherboard tray so you can access the rear-facing connectors.
If you’re considering one of these boards, make sure the case specifically lists support for that motherboard or reverse-connector layout.
Make the Right Motherboard Choice for Your Needs
Hopefully, after reading this guide, you’ll have a better idea of which motherboard form factor is right for your needs.
For most builders, the decision is fairly straightforward.
Micro-ATX is an excellent choice if you’re trying to maximize value.
ATX provides the best overall balance of features, expansion, motherboard selection, and case compatibility.
Mini-ITX is ideal if your main goal is to build the smallest possible system.
And E-ATX makes the most sense for enthusiasts and workstation users who specifically need the features offered by a larger premium motherboard.
Just remember that form factor doesn’t tell you everything about a motherboard. Two motherboards of the same size can have dramatically different chipsets, VRMs, storage options, networking, rear I/O, PCIe configurations, and prices.
Choose the form factor that fits your case and expansion requirements first, then compare the actual features of the individual motherboards you’re considering.
If you want specific motherboard recommendations, be sure to check out our motherboard buyer’s guide, as we’ve rated a bunch of the best motherboard options for each motherboard socket.
