What Is a Computer Case and Why Do I Need One?
The PC case is the final item on your initial shopping list. You need to hold all of your PC components together, protect them, and ensure that you enclose all high-frequency parts in a metal case (to avoid causing interference to other local devices, such as radios, displays, and media players).
How to Choose Suitable Case
PC cases range from plain and functional to gaming light shows, so the choice of aesthetics is extensive. There are several vital factors in choosing one:
Looks
This may be important in an office setting where a blue LED-adorned case on a desk is too distracting!
Location
Are you buying it for the top of a desk or underneath?
Cases come in several standard sizes denoted by their name, but there’s no set standard for overall dimensions:
Case Name | Rough dimensions | Typical specs | Notes |
Tower / Full Tower | 22-27” (56-69cm) high | Full capacity for large motherboards, water cooling, large PSUs. Can take ATX (and EATX - but check) motherboards. | Floor standing |
Mid / Midi Tower | 17 - 21” (43-53cm) high | A good compromise between size and parts capacity. Can take ATX motherboards. | Floor or desk |
Mini ITX, Micro ATX (mATX) | Roughly a 12.5” (316mm) cube | Mini ITX cases may only expose one external expansion slot. | Desk mounting. Limited internal space. Can be fiddly to assemble. Suitable motherboards may not support all needed features, but good for simple PCs. No room for some larger graphics cards. |
These days, it’s hard to find a horizontal desktop case, but some slim micro ATX tower cases will sit on a desk. Most suppliers offer a case search function on their website.
The case needs to hold your motherboard, PSU, and components. Reputable case manufacturers provide an instruction manual (often downloadable ahead of time) that lists supported parts' dimensions. For example:
Storage (Drive) Bays
This is partly related to case size and means the number of internal and externally-facing bays (fitting areas) the case has for hard disks, SSDs, and optical drives (e.g., DVD and Blu-ray readers/writers, if you fit any). If the case is too small, you might struggle to fit all the internal parts. Many case manufacturers will tell you how many bays are available. For example:
Form Factor
What sizes of motherboard does the case support? An ATX-sized board will not fit into a mini-ITX case, but often the reverse is true, and many have mounting holes for more than one motherboard size.
It may seem overkill to fit a small motherboard into a large case. Perhaps you are building a high-capacity storage server where you don't need a lot of processing power (so you’ve picked a mini-ITX board with integrated Celeron processor). Still, you need room (storage bays) for a lot of disk drives.
The image below is from a case instruction manual and shows which motherboard sizes are supported:
Front Panel Items
The front of the case will probably have as a minimum: a power switch, a power-on indicator LED, an HDD/SSD activity LED, a reset switch, and possibly a speaker (tastefully hidden). There may also be a range of connectors - such as USB and audio ones - for external devices. The motherboard has a row of connection pins (called headers) for these parts, and cables will be supplied with the case to connect them.
Rear Panel Items
The case will have a standard-sized, rectangular opening at the back, and your motherboard will come with a metal plate - called a shield - that fits into this opening. The shield will be punched out (contains holes!) to match all the externally-facing connectors provided by the motherboard. Typically there will be ports for audio, USB, network, and integrated graphics (if the motherboard provides this). Some motherboards have circular connectors for older styled keyboards and mice (so-called PS/2 devices).
Don’t forget to fit the shield in the case before installing the motherboard. Get it the right way up and be careful of the edges, which can be a bit sharp!
Checklist
Looking to choose a case? Remember to cover the following parameters:
Which form factor do you need? Desktop, floor (large or small tower), smaller? Consider location and what you plan to install.
Is there enough room for the cooling system? Some systems have big fan assemblies.
Is there enough room for the PSU? Some won't fit into smaller cases.
Are there sufficient storage bays? Will all the storage devices fit and how many need external-facing bays - for example, DVD / Blu-ray drives.
Your Turn!
🎯 It’s time to check the suppliers for a suitable PC case.
⚙️ Choose a case for your general office desktop PC. Also, choose a less suitable option. For both cases, note the reasons for your choice.
✅ Once you’ve finished, see how your selections compare with mine in the Example Solutions document: .docx / .odt.
Let’s Recap!
The PC case provides a safe home for the motherboard and its components, the power supply, and the internal cabling to front panel items (power and reset switch, etc.).
Various standardized case sizes are available. Your motherboard, PSU size, storage bays, and PC location (on a desk, under a desk, etc.) determine the size.
Your basic PC parts shopping list is now complete! We’ll cover some additional items later, but you’re almost ready to reach for the screwdriver and start building. Before we move on, take a little quiz to see what you’ve learned so far.
