PC Cases 101: Sizes and Layouts

Picking a PC case can be confusing at the best of times. It needs to be big enough, look good, be easy to work in, and about 50 other things. So, in the first of a few lessons, we're going to break it down for you. We'll start with case sizes and layouts. Luckily, CORSAIR makes cases of all shapes and sizes, covering a wide range of budgets, too. So, we've got plenty of examples to use in this lesson.

Size is the first thing to consider when choosing a PC case.

It needs to fit the size of your motherboard and the rest of your components. It also influences your cooling, front I/O, and how much space you have left on your desk if you plan to use it on your desktop instead of the floor. Keeping it on your desk lets you admire your gear more easily, glance at your specs if you have an LCD installed on your AIO, and prevents floor-based dust bunnies from entering your rig.

Case size standards are known as form-factors, and they don't always align with motherboard sizes. For example, a Small Form Factor case, or SFF for short, typically supports Mini-ITX and Micro-ATX, and there is also ATX form factor, which supports ATX, obviously, and sometimes E-ATX, which stands for extended ATX (it's the same length vertically but a tad bit wider).

PC Cases fall into a variety of sizes that support one or more motherboard sizes. 
Small-form-factor cases are usually limited to supporting small mini-ITX motherboards, and some support micro-ATX motherboards. Mid-Tower cases are the most popular and are able to house larger ATX motherboards. There are also full-tower cases, but they are becomingly increasingly rare these days.

At a glance, the common terms describing case sizes are:

• SFF – For the smallest PCs out there, usually Mini-ITX only but can be Micro-ATX too.
• Mini-Tower – These usually support both Mini-ITX and Micro ATX motherboards, but with a bit more space for comfort and ease of installation.
• Mid-Tower – ATX and larger motherboards, the standard desktop-sized cases.
• Full-Tower – Enormous towers that can fit any motherboard.

The larger the case, the more it can do for your component cooling due to having more fan mounts, room for air to move around, and enough space for big radiators. A larger case is also easier to build in, and larger motherboards have more connections too.


There is no consensus on "the best" size though since it depends on your preferences. A small case is going to take up less room on your desk while some of the peak SFF builds are showcases of craftsmanship and are almost works of art.

Graphics cards come in all shapes and sizes, but if you’re buying a new GPU, you’ll need to consider its size. Some AIB versions of NVIDIA® GeForce RTX™ 5090 are well over 32cm (13in) long and could have trouble fitting into some mid-tower cases depending on the configuration and sizing. For what it's worth, every modern CORSAIR case has room for the biggest GPUs available.

If you’re looking at smaller cases, you should also consider the size of the PSU. (We make PSUs of all sizes, by the way) PSUs come in many sizes, ranging from SFX (small) to SFX-L (small but a bit longer), regular ATX, and even larger. ATX PSUs are standardized in their height and width, but their lengths vary quite a bit. Check out our PC builder and see if your planned components will fit into your case.

CPUs and GPUs draw more power every year to improve on the competition and previous generations. Much has been said about the strain this puts on power supplies, but cooling is just as important.


With increased power draw comes increased heat generation, and if you want your components to deliver all the performance you paid for, make sure you have enough cooling power and airflow in your case.

• A larger computer case offers more space for a larger radiator to cool the CPU, which is the easiest way to improve CPU cooling and ensure quieter operation.
• A larger radiator surface area allows for more efficient heat transfer from the CPU to the surrounding air, with bigger cases having support for goliath 420mm radiators.

Finally, choosing an AIO cooler with a large radiator provides better cooling performance than air coolers, because liquid has a higher heat capacity than air, and a radiator mounted on the side of the case blows heat out of the case rather than letting it gather inside.

The 2800X RS-R is our smallest case currently, and though it's made for Micro ATX motherboards it also supports Mini-ITX as well, but we imagine most people will use it as intended due to its size. Despite its compact footprint it still supports a 360mm radiator in the roof and GPUs up to 365mm in length, so it can be a formidable gaming machine quite easily. It is essentially a shrunken 3500X, but about two inches shorter in vertical length so it easily fits onto a desk.

We sell a variety of mid-tower cases and they are all considered standard ATX cases in that they are towers that support ATX motherboards, which is the majority of DIY PCs these days. The FRAME 4000D is our standard-bearer in this category as it's the size people expect when looking for a tower case, whereas the FRAME 5000D is a bit larger in every dimension, but not quite big enough to be a full-tower case.

The full-tower case is a behemoth and is usually chosen by those who want to run a custom cooling loop, or two. There is enough room for multiple radiators, pumps, tubing, and so forth, so you could use liquid to cool both your CPU and GPU for the pinnacle of PC cooling performance.