How To Build A PC

The Tom’s Hardware community is a very diverse community, ranging from those with extensive computer experience to those just starting out. Either way, if you've never built your own PC, the process can seem daunting. Fortunately, many of us at Tom’s Hardware build PCs as part of our daily work, so we like to share the knowledge we've gained.

Because there are so many parts and options to choose from, any good build starts with well-defined purpose. Whether you're building a high-end gaming PC, a workstation, or a sleek new home theater system, or anything in between, each build is going to have its own special set of requirements. Those requirements will eventually influence the decisions made later on in the build process, so it’s important to have them in hand before you start. Once you've hashed out the purpose behind the build, it's time to start selecting parts, starting with the case.

For seasoned builders, it may seem odd that we’re starting off by picking the case before everything else. However, the purpose for the build often dictates the type of case, and even if it doesn’t, we’ve found that it’s easier later on to choose components that will fit inside of a given case, instead of trying to find a case that will fit around a given set of components.

You can find specifications for most of the popular case sizes below. It’s worth noting that we use the term specifications loosely here and that these numbers serve as more of a guide than a standard. In previous times these categories used to be defined by how many 5.25” drive bays a case had, but as technology has changed they’ve evolved to be defined more by a case’s over all height and motherboard support.

Traditional Case Sizes
TypeFull TowerMid TowerMini TowerMini CubeDesktop
Height21-24 inches17-19 inches12-14 inches7-9 inches3-7 inches
Width6-8 inches6-8 inches6-8 inches8-9 inches14-17 inches
5.25" bays4-9
3-61-21-21-3
3.5" internal bays6-122-61-21-22-4
Motherboard Form FactorATX, EATXATXmicroATXmini-ITXATX, microATX
Card slotsSevenSevenFourTwo2-7
Power supplyPS/2 or largerPS/2PS/2 or SFXSFX or TFXVarious

Full towers are about as large as cases get before you start to venture off the beaten path and into the realm of super specialized applications like bitcoin mining, extreme overclocking, or tower servers. They usually come with enough room for E-ATX and ATX motherboards, anywhere from four to nine 5.25” drive bays, and plenty of room for the largest graphics cards and other components. They also come with the space required to store all of the cooling equipment necessary for a case packed full of high performance equipment.

All of that space may sound great, but the main downside to full tower cases is that they’re so large internally that most mainstream users, and even many enthusiasts, just don’t have enough gear to make efficient use of that space.

ATX mid-towers are by far the most popular choice for most mainstream and enthusiast builds, typically because they usually provide the best performance-per-dollar value ratio in terms of cost and available space. Most well-designed models will come with enough room for a full size ATX motherboard and PS/2 power supply, several hard drives and optical drives, and several expansion cards, all without occupying an inordinate amount of space. Speaking of expansion cards, most mid-towers will come with seven expansion slots, which should provide ample space for two dual-slot graphics cards, as well as some additional space for other expansion cards like WiFi, USB and more.

Notice how we said there was room for only two dual slot graphics cards? Even though many mid-tower cases do have enough room for three or even perhaps four graphics, we don’t recommend such configurations due to the heat and space issues that usually arise. If you’re dead set on a three or four-way SLI or Crossfire setup, then a full tower case is likely a much better choice.

MicroATX mini-towers are a more refined and compact version of their larger mid-tower counterparts. They are mainly used in business settings and for portable gaming rigs where all-out performance is less of a priority than having a case with a smaller footprint and that is easier to transport. Mini-towers often come with support for at least one 5.25” optical drive and several hard drives. Finally, since microATX motherboards support a maximum of four expansion slots, most mini-towers can support up to two dual-slot graphics cards, depending on the capabilities of the motherboard.

Mini-ITX cubes and towers come in a variety of shapes and sizes, with their key feature being that they only support mini-ITX motherboards and therefore usually impose the most limitations on which parts can be used. The advantage is that mini-ITX cases are very space efficient and usually present a minimal footprint, which makes them popular in office environments and for ultra-portable gaming rigs. Typically, they only support SFX form factor power supplies, although an increasing number of cases support small PS/2 power supplies. Mini-ITX cases generally lack support for 5.25” optical drives, though many do have enough room to support a thin, slot-loading optical drive. Finally, mini-ITX cases have a maximum of two expansion slots, which limits them to, at most, a single, compact graphics card.

Desktop/HTPC cases represent the style of case that used to sit underneath monitors to raise them up to eye level. Nowadays they’ve mainly been relegated to use as HTPC (home theater PC, or media center PC) chassis, where they’ve flourished. They come in a variety of sizes, from something so small it needs an external power supply, to mid-size mini-ITX cases like the Raven RVZ01 (pictured bottom-center, above), to what are essentially horizontal mid-tower cases. Many of the HTPC cases available usually support a horizontally-mounted, full-size graphics card through the use of a riser card.

If you want to go even smaller than the examples above, that small yellow box (also pictured above) is called the Brix Pro, and it’s the smallest unit we’ve tested, aside from a NUC (Next Unit of Computing, or a mini PC). It comes with support for two notebook-size memory modules, an on-board mSATA SSD, and room for a 2.5” SSD or hard drive. If that’s still not small enough, then consider buying an NUC, which is even smaller. Most NUCs come as a complete computer, finished off by adding your choice of notebook-size memory and a 2.5” SSD or hard drive.

By this point, you should have a pretty good idea of what the purpose of your build is and what size of case you want to get. If you need a bit of help picking the perfect case, we’ve got you covered with a list of the best computer cases for the money.

MORE: Best Cases
MORE: Cases in the News

MORE: All Case Content

MORE: Cases in the Forums

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32 comments
    Your comment
  • AndrewJacksonZA
    "the power supply is actually one of the more important parts of a build"
    Thank you!!

    Or rather, let's do what the cool kids are doing and rather post a GIF:
    https://giphy.com/gifs/the-office-thank-you-michael-scott-1Z02vuppxP1Pa
    3
  • Eggz
    Great piece for a lot of first-time builders. This should have a sticky somewhere on the site so it doesn't get buried :-)
    5
  • jkhoward
    Quote:
    "the power supply is actually one of the more important parts of a build" Thank you!! Or rather, let's do what the cool kids are doing and rather post a GIF: https://giphy.com/gifs/the-office-thank-you-michael-scott-1Z02vuppxP1Pa


    Seriously, not enough people realize how import a good PSU is. I am working with someone is heavily overclocking an i7 and two 970 in SLI as well as 4 SSD and a few hard drives, a bunch of fans, with a 750W PSU.
    -2
  • jkhoward
    Also... I am digging the age of some of these images.
    4
  • alidan
    Quote:
    Quote:
    "the power supply is actually one of the more important parts of a build" Thank you!! Or rather, let's do what the cool kids are doing and rather post a GIF: https://giphy.com/gifs/the-office-thank-you-michael-scott-1Z02vuppxP1Pa
    Seriously, not enough people realize how import a good PSU is. I am working with someone is heavily overclocking an i7 and two 970 in SLI as well as 4 SSD and a few hard drives, a bunch of fans, with a 750W PSU.


    unless i'm thinking wrong, isn't that within the power limits of a 750? im even assuming that each gpu is 300 watts and i know they shouldn't hit that even with the most aggressive of ocs

    granted there is a distinction between a good psu and a bad one, but im just assuming its a good one.
    3
  • chimera201
    Motherboard slots haven't evolved much. Wished every slot was like a USB slot
    0
  • turkey3_scratch
    612443 said:
    Seriously, not enough people realize how import a good PSU is. I am working with someone is heavily overclocking an i7 and two 970 in SLI as well as 4 SSD and a few hard drives, a bunch of fans, with a 750W PSU.


    Your point being... ?
    3
  • renosablast
    Steps 1 and 3 should be combined, and step 2 comes after 1 and 3. You better worry about the CPU and motherboard combo compatibility before you worry about a graphics card.
    -1
  • renosablast
    Sorry, meant steps 2 and 4 before 3.
    0
  • SR-71 Blackbird
    I love when you see a $1500.00 build with top quality components and then they have a $40.00 PSU listed with it.
    5
  • Outlander_04
    IMO the very first component selection for a gaming build should always be the .... MONITOR.
    Decisions on where and how to spend the rest of the budget can only be made once you know the resolution , and whether its 60 Hz, 144 Hz or whatever else is available
    1
  • MasterMace
    Gonna throw in my disagreement on the priority, mentioned nice and early in the article. The first thing you pick is never your case. There's 3 things you can decide to be your starting point when building a pc to make it a smooth ride; either, 1. Budget. 2. CPU 3. Graphics. By picking 1 of these 3 things as your starting point, you can have a very smooth build process. Does that mean you buy your case last? No, I've seen plenty of builds where the case arrives first as a way of storing the items, but when you want a solid build, your case is last priority, as it has no impact on your performance and restricts the size of your items.

    Even if you wanted to build an odd form factor, like an itx, you would still pick the cpu or the budget before the case.
    2
  • MrXtreme
    Thank you for explaining ESD correctly. I have been annoyed with articles over exaggerating about ESD a lot. So just touching something metal can help? Well, next time I think I'll set a PC on my wooden desk instead of the carpet.
    0
  • kunstderfugue
    Quote:
    I love when you see a $1500.00 build with top quality components and then they have a $40.00 PSU listed with it.


    The XFX TS Bronze 550 comes down to $43 ish from time to time and that's a mighty fine PSU to power a single graphics card build.
    0
  • nitrium
    Quote:
    "the power supply is actually one of the more important parts of a build" Thank you!!

    While not unimportant, it gets far too much attention on the forum's here. PSU's are only relatively rarely the cause of issues, and I'll go out on a limb and say that virtually ANY modern 650W PSU (even ultra-cheap China garbage) will reliably power a single GPU and CPU, regardless of model or how much OCing you do to them.
    -3
  • Crashman
    269694 said:
    Quote:
    I am working with someone is heavily overclocking an i7 and two 970 in SLI as well as 4 SSD and a few hard drives, a bunch of fans, with a 750W PSU.
    unless i'm thinking wrong, isn't that within the power limits of a 750? im even assuming that each gpu is 300 watts and i know they shouldn't hit that even with the most aggressive of ocs granted there is a distinction between a good psu and a bad one, but im just assuming its a good one.
    You're exactly right. We've been using high-quality power supplies in most of our System Builder Marathon machines, and dual 970s was in one of the builds. The super-high recommendations you see from other sites are a response to most builders using mediocre-quality units.
    1
  • Crashman
    416912 said:
    Gonna throw in my disagreement on the priority, mentioned nice and early in the article. The first thing you pick is never your case. There's 3 things you can decide to be your starting point when building a pc to make it a smooth ride; either, 1. Budget. 2. CPU 3. Graphics. By picking 1 of these 3 things as your starting point, you can have a very smooth build process. Does that mean you buy your case last? No, I've seen plenty of builds where the case arrives first as a way of storing the items, but when you want a solid build, your case is last priority, as it has no impact on your performance and restricts the size of your items. Even if you wanted to build an odd form factor, like an itx, you would still pick the cpu or the budget before the case.
    Exactly wrong. The first thing people do is say "I want a LAN box" or "I want a media player" or "I want a big gorgeous office PC". They're picking a case SIZE when they make those FIRST statements, so size comes first in the discussion.
    1
  • beoza
    Quote:
    416912 said:
    Gonna throw in my disagreement on the priority, mentioned nice and early in the article. The first thing you pick is never your case. There's 3 things you can decide to be your starting point when building a pc to make it a smooth ride; either, 1. Budget. 2. CPU 3. Graphics. By picking 1 of these 3 things as your starting point, you can have a very smooth build process. Does that mean you buy your case last? No, I've seen plenty of builds where the case arrives first as a way of storing the items, but when you want a solid build, your case is last priority, as it has no impact on your performance and restricts the size of your items. Even if you wanted to build an odd form factor, like an itx, you would still pick the cpu or the budget before the case.
    Exactly wrong. The first thing people do is say "I want a LAN box" or "I want a media player" or "I want a big gorgeous office PC". They're picking a case SIZE when they make those FIRST statements, so size comes first in the discussion.


    I have to agree with you on this Crashman. Whenever I go to build a new system for friends or relatives I always ask what they're going for in terms of use. I like to go with the Form follows function principle which is that the shape of a building or object should be primarily based upon its intended function or purpose.
    0