Start with these seven core components

A working computer needs a motherboard, CPU (processor), RAM (memory), storage drive, power supply, case, and cooling solution. Everything else — graphics cards, extra fans, wireless cards — plugs into or sits alongside these seven. If any one is missing or broken, the computer will not start.

The motherboard is the circuit board that everything connects to. The CPU is the processor that does the actual work. RAM is fast temporary memory that programs use while running. The storage drive (SSD or hard drive) holds your files and operating system permanently. The power supply converts wall power into the right voltage for each component. The case holds everything together and protects it. The cooling solution — usually a fan or liquid cooler attached to the CPU — keeps the processor from overheating.

You will also need a monitor, keyboard, and mouse to actually use the computer once it is built, but those are not part of the computer itself. A copy of Windows, Linux, or another operating system is also necessary before the computer is useful, though you can install it after assembly.

Key Takeaways

  • A motherboard, CPU, RAM, storage drive, power supply, case, and CPU cooler are the seven parts required for any working computer.
  • The motherboard socket type must match your CPU, and the power supply wattage must be enough for all your components combined.
  • RAM capacity and storage size depend on what you plan to do — gaming, video editing, or everyday browsing each have different needs.
  • A case must have room for your motherboard size and your chosen cooler, and the power supply must fit inside it.
  • You will need a monitor, keyboard, mouse, and an operating system to use the computer, but these are separate purchases from the core build.

CPU and motherboard must match each other

The CPU plugs into a socket on the motherboard, and the socket type must match the processor you buy. Intel and AMD are the two main CPU makers, and they use different sockets. Intel currently uses LGA1700 for newer processors, while AMD uses AM5. Older systems use different sockets (LGA1200, AM4, and others), so if you are reusing an old motherboard, you must buy a CPU that fits that socket.

The motherboard also determines what RAM type you can use. Modern boards use DDR5 or DDR4 memory — the two are not interchangeable. Older boards use DDR3 or earlier. When you choose a motherboard, check its specifications to see which socket it has and which RAM type it accepts, then buy a CPU and RAM that match.

Motherboards come in three sizes: ATX (full-size), Micro-ATX (medium), and Mini-ITX (small). The size affects what case you need and how many expansion slots you have. For a first build, ATX or Micro-ATX are easier to work with because components have more room.

RAM capacity depends on what you do

RAM is measured in gigabytes (GB). For everyday tasks like web browsing, email, and document editing, 16 GB is standard and sufficient. For gaming, 16 GB is still the baseline, though some newer games benefit from 32 GB. For video editing, 3D rendering, or running many programs at once, 32 GB or more is common.

RAM also comes in different speeds, measured in MHz. Faster RAM can improve performance slightly, but the difference is usually small compared to having enough capacity. For most builds, standard-speed RAM at your motherboard's rated speed is fine.

You can always add more RAM later if you need it, as long as your motherboard has empty slots. Most modern boards have two or four RAM slots. Check your motherboard's specifications to see how many slots it has and what the maximum capacity is.

Storage size and type affect speed and cost

An SSD (solid-state drive) is faster and more reliable than an older HDD (hard disk drive). SSDs have no moving parts, so they are quieter and less likely to fail. For a new build, use an SSD as your main drive. A 500 GB SSD is the minimum for an operating system and a few programs, but 1 TB (1,000 GB) is more practical if you store files locally. If you work with large video files, photos, or games, 2 TB or more is common.

SSDs connect via NVMe (the fastest type, plugs directly into the motherboard) or SATA (older, uses a cable). NVMe drives are faster and cheaper now, so they are the standard choice. Check your motherboard to see how many NVMe slots it has — most modern boards have at least two.

You can add a second drive later for extra storage without replacing the first one. Many people use a fast 1 TB NVMe drive for the operating system and programs, then add a larger HDD or second SSD for files and backups.

Power supply wattage must cover all components

The power supply converts electricity from the wall outlet into the right voltage for your components. Its wattage (measured in watts, or W) must be enough for everything you are running at once. A basic office computer might need 300 to 400 watts. A gaming computer with a high-end graphics card might need 750 to 1000 watts.

To estimate your needs, add up the power draw of your CPU and graphics card (both listed in their specifications), then add 20 to 30 percent as a safety margin. A power supply rated for more wattage than you need is fine — it will not waste power, and it gives you room to upgrade later.

Buy a power supply from a reputable brand. Cheap power supplies can fail suddenly and damage your components. Look for 80+ Bronze certification or higher, which means the power supply is reasonably efficient. The brand matters more than the exact wattage — a 650-watt supply from Corsair or Seasonic is safer than a 1000-watt supply from an unknown maker.

The case must fit your motherboard and cooler

The case holds all your components and protects them from dust and damage. Case size must match your motherboard size: an ATX case fits ATX boards, a Micro-ATX case fits Micro-ATX boards, and so on. A larger case can hold a smaller motherboard, but a smaller case cannot hold a larger one.

The case must also have enough vertical space for your CPU cooler. Most air coolers are 150 to 160 millimeters tall. If your case has a maximum cooler height of 140 mm, a standard air cooler will not fit. Check both the case specifications and the cooler height before buying.

Cases also vary in how many fans they come with and how many you can add. A case with good airflow keeps components cooler and quieter. For a first build, any case from a known brand (Corsair, NZXT, Fractal Design, Lian Li) will work fine. Avoid very cheap cases — they often have sharp edges and poor cable management space.

CPU cooling keeps the processor from overheating

Every CPU needs a cooler. The cooler sits on top of the processor and pulls heat away. There are two main types: air coolers (a fan with metal fins) and liquid coolers (a pump that circulates water through tubes).

Air coolers are simpler, cheaper, and reliable. They work well for most builds, including gaming. Liquid coolers are more expensive and require more maintenance, but they cool better and look more impressive. For a first build, an air cooler is the practical choice. Popular models include the Noctua NH-D15, be quiet! Dark Rock Pro 4, and Thermalright Peerless Assassin.

Some CPUs come with a stock cooler in the box, but it is usually basic and loud. Buying a better aftermarket cooler is worth the cost if you plan to keep the computer for years. The cooler must be compatible with your CPU socket — check the manufacturer's website to confirm before buying.

Peripherals and software complete the setup

Once the computer is built and running, you need a monitor to see what is happening, a keyboard to type, and a mouse to navigate. These are not part of the computer itself, but you cannot use it without them. A basic 1080p monitor costs $100 to $200. A mechanical keyboard and mouse together cost $50 to $150, though cheaper options exist.

You also need an operating system. Windows 11 is the most common choice and costs around $120 for a full license, though you can install it free with a watermark and some limitations while you decide. Linux is free and open-source, and works well for many tasks. macOS only runs on Apple computers.

Before you buy anything, make a list of the seven core components with specific models, then check that each one is compatible with the others. Websites like PCPartPicker will flag incompatibilities automatically — motherboard socket, RAM type, case size, and cooler height are the most common issues.

Frequently Asked Questions

Can I reuse parts from an old computer?

Yes, if they are compatible. An old power supply might not have enough wattage for new components, and an old motherboard might not accept modern CPUs or RAM. The case, monitor, keyboard, and mouse usually work fine with a new build. Check the specifications of any old part against your new components before reusing it.

What if I do not know the wattage my power supply needs?

Use an online calculator like OuterVision or be quiet!'s power calculator. Enter your CPU and graphics card models, and it will estimate the wattage you need. Then buy a power supply rated for about 20 percent more than that estimate.

Do I need a graphics card?

Not always. Many modern CPUs have built-in graphics that work for everyday tasks, web browsing, and light gaming. If you want to play demanding games or do 3D rendering, a dedicated graphics card is necessary. Check your CPU's specifications to see if it has integrated graphics.

Can I upgrade parts later?

Yes. RAM, storage drives, and graphics cards are straightforward to add or replace. The CPU and motherboard are harder to change because they are connected to everything else. Buy a good motherboard and power supply now, and you can upgrade the other parts as your needs change.

What tools do I need to build it?

A Phillips head screwdriver is the only tool you really need. An anti-static wrist strap prevents accidental damage to sensitive components, though it is not required if you touch the case regularly to discharge static. Most people build without one and have no problems.