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Motherboard Form Factor Guide – Logical Increments Blog

Computer cases can come in a wide array of shapes and sizes, from a basic box you can order online to a custom-made bust of your uncle Kevin that you can slap a power supply and graphics card into.

No matter what kind of case you gravitate towards, it is important to know what form factor of motherboard will be compatible with it, and the benefits and drawbacks that accompany those sizes. Whether you are building a new PC or simply upgrading ol’ reliable, the form factor of your motherboard is an important piece of the puzzle.


What is a Form Factor?

It’s a size. A form factor is a standardized size that any motherboard can be categorized into. To be considered a micro ATX motherboard, for example, it must have the same size, same mounting screw locations, and same placement of certain ports as all other micro ATX motherboards (with some minor exceptions). This allows for widespread compatibility of motherboards and cases from different manufacturers. In addition, a motherboard of a specific form factor can fit into some larger form factor cases, due to the consistency of mounting screw locations, but the reverse is not true. As shocking as it may be, an “Extended ATX” motherboard will not fit into a “micro ATX” case!

Different form factors suit different styles of PCs: larger motherboards are more powerful and possess more features, but generally demand higher price tags and always require larger cases. Smaller form factors can produce quiet, compact PCs, but with some sacrifices in terms of performance and compatibility.

Let’s take a closer look at the benefits and drawbacks of some of the most popular motherboard form factors on the market! We’ll start with the most common and work down to the rarer types, listing off specs and some pros and cons for each as we go.


Common Form Factors

Guide] Motherboard Form factors & Sizes - OC3D Forums


The basic form factor since its introduction by Intel in 1995, the standard ATX form factor is the bread and butter of the consumer computing world. Most motherboards produced are of standard ATX size, and the mid-tower cases made to hold them are in no short supply (yet). These motherboards are relatively large, measuring 305 millimeters tall and 244 millimeters wide; that’s about an inch wider and taller than an ordinary piece of printer paper. They offer a great balance between functionality and price that meets (or often exceeds) the needs of the average consumer. These motherboards will fit into a case designated either “ATX” or “mid-tower”, but they can also fit into larger EATX or “full tower” cases as well, just with some extra space left over.




    • Size: 305mm x 244mm | 12” x 9.6”
    • Average CPU sockets: 1
    • Average RAM slots: 4
    • Max PCI slots: 7
    • Average SATA ports: 6-12
    • Compatible cases: Mid-tower (ATX), Full tower (EATX)


    • Very common, huge market selection
    • Plenty of RAM and PCI slots
    • Good price-to-performance ratio


    • Modern chipsets and features can be pricey
    • Can only fit mid-tower or larger cases


Standard ATX motherboards are primarily recommended for those desiring a gaming computer or a normal office PC. The large number of PCI slots allows for a bevy of graphics cards, sound cards, and other hardware to be installed (depending on the specific motherboard’s slot types). Four RAM slots allow for extensive memory capacity, perfect for demanding workstation activities or gaming while you have other tasks open on multiple monitors. But the relatively large size of this form factor means that you are usually restricted from using a case smaller than a mid-tower, which may or may not introduce issues into your build.

Micro ATX

The Micro ATX form factor is essentially a standard ATX motherboard shortened into a square at the expensive of losing three PCI slots. This form factor is compatible with ATX cases and power supplies, and often uses the same chipsets as their full-sized brethren. Measuring 9.6” tall as well as wide, these squat motherboards are excellent options for budget builds as their lower number of PCI slots and relatively weaker overclocking performance knocks the price down a few notches. Adding to their value is their versatility: in addition to micro ATX mini towers, micro ATX motherboards can fit into any mid- or full tower case that supports other ATX form factors… if you can stomach the unused space.




    • Size: 244mm x 244mm | 9.6” x 9.6”
    • Average CPU sockets: 1
    • Average RAM slots: 4
    • Max PCI slots: 4
    • Average SATA ports: 4-8
    • Compatible cases: Micro-ATX, Mid-tower (ATX), Full tower (EATX)


    • Fits into all but the smallest cases
    • Cheaper than other popular form factors


    • Fewer PCI slots than standard ATX
    • Often use weaker VRMs, which impedes overlocking


The Micro ATX form factor can be recommended to those looking for features similar to standard ATX on a budget. Motherboards of this form factor typically sport the same number of CPU and RAM slots as a standard ATX board but at a lower price. While there’s fewer maximum PCI slots comparatively, four is still plenty for most consumers looking to build a gaming PC. However, reduced overclocking potential means that you will not be able to push these motherboards to the level of performance you would find in standard ATX or EATX.


Originally created as a compact motherboard that forgoes the need for cooling fans (typically no longer true), the mini-ITX is the smallest form factor recommended for PC building. Despite the ITX designation, mini-ITX motherboards are generally still compatible with all sizes of ATX cases, including micro-ATX, mid-tower, and full-tower. These tiny square boards are just above 6” long on both sides—an ultra-small board perfect for small-footprint PCs where emphasis is placed more on appearance, space efficiency, or portability than on raw power. Sporting a single PCI slot and two RAM slots means carefully selected, efficient hardware is a must if you plan on gaming with a mini-ITX motherboard.



    • Size: 170mm x 170mm | 6.7” x 6.7”
    • Average CPU sockets: 1
    • Average RAM slots: 2
    • Max PCI slots: 1
    • Average SATA ports: 2-6
    • Compatible cases: Mini-ITX, Mini tower (Micro-ATX), Mid-tower (ATX), full tower (EATX)


    • Impressively small and easily transported
    • Generally highest compatibility of all motherboard types


    • Only two RAM slots and a single PCI slot
    • Can cost as much as a standard ATX motherboard
    • Looks frightened and alone inside a mid- or full tower case


Mini-ITX is a niche form factor that sacrifices performance for an ultra-compact design. These motherboards are typically used by enthusiasts who place form far above function. While potentially elegant and minimalistic, this form factor can be difficult to utilize while on a budget. They are often price similarly to a standard ATX motherboard despite having far fewer hardware slots. If building a gaming PC, the single PCI slot must be reserved for your graphics card, and a bulky card can impede airflow in such small cases. Two RAM slots can also make gaming or multi-tasking difficult without expensive high-capacity RAM. That being said, this form factor can produce some spectacular, simple PCs or highly portable workhorses if you find the right case and don’t mind the extra build difficulty.

Extended ATX

Tremendously powerful, tremendously expensive, tremendously… tremendous! The extended ATX form factor is at the apex of consumer performance. It’s the same height as a standard ATX board, but much wider. This form factor can support eight total PCI slots, up to eight sticks of RAM, and frequently twin CPUs all at once. The only case that extended ATX will fit into is a full tower case with eight expansion slots.






    • Size: 305mm x 330mm | 12” x 13”
    • Average CPU sockets: 1-2
    • Average RAM slots: 8
    • Max PCI slots: 8
    • Average SATA ports: 6-16
    • Compatible cases: Full tower (EATX)


    • Unrivaled performance and potential
    • Some models support two CPUs. Yes, two whole CPUs at once!


    • Several times the price of a standard ATX motherboard
    • Relatively few models to choose from
    • Can only fit in a full tower case


The few EATX motherboards on the market are reserved for the beefiest gaming computers and most serious of workstation builds, and they command a high price for their status. These motherboards are exclusively recommended to those with business to conduct or money to burn; to put this form factor to proper use, you’ll need (at least one) high-tier CPU, eight sticks of RAM, and (at least one) top-of-the-line graphics card. In today’s climate of hardware prices, a PC of this magnitude could easily cost ten billion dollars. Well, maybe not… but it’ll empty your wallet nonetheless!



There you have it: four form factors to choose from when putting together your next PC. While there’s dozens more form factors out there, these are definitely the ones you’ll see most often in the wild. Not only are they mostly compatible with the same cases as each other (space permitting), but also with most other components on the market.

Whether you’re interested in a tiny mini-ITX or a gargantuan extended ATX, we hope this guide has made the selection process a little bit easier. Let us know which form factor you favor, and why, in the comments below!

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