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Building a PC for the first time: what do you need to buy?

The first question anybody building their own machine asks is "what do I need to buy?" The short answer is six parts every machine needs, plus two more that depend on which CPU you pick.

3 min read · last updated 2026-09-11

The six every machine needs

Whatever the budget, a machine cannot be assembled without these six. Miss one and it does not start — not "runs slower", does not start.

CategoryWhat it does
CPUThe processor. It decides which socket the motherboard must be.
MotherboardThe board everything plugs into. It decides which memory you can use.
MemoryWorking memory. DDR4 and DDR5 are not interchangeable.
StorageAn SSD or hard disk for Windows and your files.
Power supplyPowers everything. It has to supply enough.
CaseThe box it all goes in. It decides how long a graphics card can be.

Two more that depend on the CPU

These two are not always required. Whether they are depends on which CPU you chose — and this is where beginners are caught out most often.

A graphics card. Many CPUs have graphics built in (an iGPU) and can drive a monitor straight from the motherboard. Models ending in F do not — Intel Core i5-14400F and AMD Ryzen 5 7500F, for instance. Build either of those without a graphics card and the finished machine puts nothing on the screen.

A cooler. Some CPUs include one in the box and some do not. Intel Core i5-14400F does; AMD Ryzen 5 7600X and Intel Core i5-14600K do not, and you have to buy one. The detail is in Which CPUs come with a cooler?

An order of choosing that avoids backtracking

PC parts are not independent of one another. Choosing one eliminates options for several others. Work in this order and you rarely have to go back.

  1. CPU — always first, because it locks the motherboard’s socket and usually the memory type as well.
  2. Motherboard — matching the CPU’s socket. Now you know whether it is DDR4 or DDR5, and what size the board is.
  3. Memory — the type the motherboard takes.
  4. Case — it has to accept that board size, and the card length it takes becomes the ceiling for the next step.
  5. Graphics card — no longer than the case allows.
  6. Power supply — you now know what the CPU and card draw, so you can size the watts; and it has to be a body size the case accepts.
  7. Storage — check how many M.2 slots the motherboard has.
  8. Cooler — it has to support the CPU’s socket and be short enough for the side panel to close.

A worked example, already checked

The build below passes the same rules the build page uses. Open it and change parts one at a time — it will tell you straight away if a change makes something incompatible.

A first machine that games, with nothing missing

This CPU has no built-in graphics and no bundled cooler, so both have to be in the list.

✓ No problems found330W draw · 550W PSU advisedOpen on the build page →

Things you need that are not on this list

This site checks only the parts inside the machine. Assembled and working, it is still not usable without these.

  • Monitor, mouse, keyboard — no compatibility questions here; anything works.
  • Windows — a separate licence, or Linux, which costs nothing.
  • Thermal paste — almost every cooler includes some, or arrives with it pre-applied. No need to buy more for a one-off build.
  • Mains cable — the power supply comes with one.

Try building one yourself

Incompatible parts are filtered out from the start, and every "will not work" comes with the reason.

Start a build →

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