You can ensure that your new motherboard fits inside your case by purchasing a motherboard of the appropriate form factor. The form factor information about your motherboard may be found in the documentation that came with it.
If you already own a full-tower case, you won’t need to worry about whether or not your new motherboard will fit into the case. That’s because all sizes of motherboards fit into a full-tower case. Conversely, a standard ATX motherboard cannot fit into a mini-itx case.
Let’s look at why.
We recommend learning the case size before shopping for a motherboard. If you intend to build a new computer from parts, you need to choose your motherboard first, then choose your case unless you want a full tower case that even supports E-ATX motherboards.
While this might seem arduous, open the case anyway to review its current parts. This is especially true if you built your computer a few years ago or had another party do so.
Motherboard sizes range from Mini-ITX to micro-boards to XL-ATX. The latter might sound like shopping for sweatpants, but don’t worry. I have yet to see an XXXL ATX in salmon pink.
Mini ITX measures 6.7 in. x 6.7 in. (170 mm. x 170 mm.)
Standard ATX measures 12 in. × 9.6 in. (305 mm. × 244 mm.)
Micro ATX measures 9.9 in. × 9.9 in (244 mm. × 244 mm.)
Flex ATX measures 9 in. × 7.5 in (229 mm. × 191 mm.)
Extended ATX (E-ATX) measures 12 in. × 13 in. (305 mm. × 330 mm.)
Extended ATX measures either 12 in. × 10.1 in. (305 mm. × 257 mm.) or 12 in. × 10.4 in. (305 mm × 264 mm) or 12 in. × 10.5 in (305 mm. × 267 mm.) or 12 in. × 10.7 in (305 mm. × 272 mm.)
Enhanced Extended ATX (EE-ATX) 13.68 in. × 13 in. (347 mm. × 330 mm.)
Ultra ATX measures 14.4 in. × 9.6 in (366 mm. × 244 mm.)
XL-ATX measures 13.5 in. × 10.3 in. (343 mm. × 262 mm.) or 13.58 in. × 10.31 in. (345 mm. × 262 mm.) or 13.6 in. × 10.4 in. (345 mm. × 264 mm.)
So, you can see that even if your case says it can house an Extended ATX, you need to know the exact measurements of the case, so you choose a board that fits inside it. So, let’s look at the most common case sizes.
Case Size Options
You can choose from one of three standard sizes of cases, or from a fourth option, referred to as a smaller form factor(SFF). As creative as computer manufacturers sometimes get with names, they didn’t manage it with form factor names for cases. Just as it sounds, it is smaller than the others.
Smaller Form Factor Cases
These towers vary in size, but a few things stay the same. You’ll only have space for one graphics card and two expansion slots. These towers only provide space for one to three drive bays. You can fit a mini-ITX motherboard in these.
Also referred to as a standard-sized case or full tower, you can purchase any size motherboard and it will fit in this size case. The most common choice would be a standard-sized ATX, but you could also use a Mini-ITX, MicroATX, or EATX. You’ll have room for up to eight case fans in this tower and three to four graphics cards.
In a mid-tower, you lose some flexibility on motherboard sizes. You can use a Mini-ITX, MicroATX, or ATX in these cases. You’ll still have room for three to eight case fans, up to three graphics cards, and five to seven expansion slots.
Also referred to as a mini-tower, your tiny case can only accommodate a tiny motherboard. Choose a mini-ITX or microATX to squeeze into this size box.
What Does This Mean for Your Shopping?
Always think ahead before upgrading. What you purchase today will probably get outpaced next month. You may quickly want to upgrade. You purchase a standard case to start with, you can upgrade to any motherboard, as long as you have the power supply for it. Your motherboard typically plugs directly into your power supply.
Rather than considering what power users consider the top of the line now, consider what you would upgrade. Can the motherboard you choose accept memory upgrades? How much memory and of what type?
Here, your budget comes into play. The best choices of motherboard will let you zip through your computing needs now and upgrade later. High-end motherboards typically cost more than $250. They also only come in the standard ATX size.
Under $150, you sacrifice upgrades to affordability. This means you can buy these boards in mini, micro, or standard size, but you won’t get to overclock it, nor will your motherboard offer RGB lights, expansion slots, or an impressive heat sink.
All of those bells and whistles require more room. That’s why the top-of-the-line motherboards only come in standard ATX and cost you about $250 or more.
What if My Case Said a Form Factor Fits and It Doesn’t?
This can happen although it isn’t a good thing when it does. Manufacturers create the form factor specification stickers based upon the currently available models of each part. Occasionally, a manufacturer changes things after the sticker gets slapped on the box and sold.
You return the motherboard to the vendor from which you purchased it and exchange it for a different one. Knowing which one to buy comes down to doing a bit of research online if you had to return an ill-fitting or just-not-fitting-in motherboard.