What You Actually Need to Build a PC

A working PC requires seven components: a motherboard, a CPU (processor), RAM (memory), a storage drive, a power supply, a case, and a cooling system. Everything else—graphics cards, extra fans, wireless cards—is optional depending on what you plan to do. You cannot skip any of these seven, and the order you buy them matters because some decisions lock in others.

The motherboard is your starting point. It is the circuit board that every other part plugs into, and it determines which CPU, RAM, and cooling system will physically fit. Once you pick a motherboard, your CPU choice narrows down to one socket type. Once you pick a CPU, your cooling system must match that socket. This is why builders usually start with either the motherboard or the CPU—pick one, and the other choices follow.

Key Takeaways

  • The motherboard is your anchor decision because it determines which CPU socket, RAM type, and cooling mount will work with your build.
  • A CPU and cooling system must match: the CPU generates heat, and the cooler must be rated for that CPU's power output and fit its socket.
  • RAM and storage are separate—RAM is fast temporary memory that clears when you shut down, and storage is permanent space for files and programs.
  • The power supply must have enough wattage for your CPU and GPU combined, plus a 20 percent safety margin, and it should be 80+ Bronze rated or better.
  • The case holds everything and provides airflow; pick one that fits your motherboard size and has room for your cooling system and storage drives.

The Motherboard: Your Foundation

The motherboard is a large circuit board with slots and sockets for every other component. It has a CPU socket (where the processor sits), RAM slots (usually two to four long vertical slots), a power connector, storage connectors, and a chipset that manages communication between parts. When you shop for a motherboard, you are really shopping for a CPU socket type and a form factor.

Form factor is the physical size. The three common sizes are ATX (full-size, about 12 by 10 inches), Micro-ATX (smaller, about 9 by 8 inches), and Mini-ITX (smallest, about 6.7 by 6.7 inches). Smaller boards fit in smaller cases and use less power, but they have fewer RAM slots and storage connectors. Your case must fit your motherboard size, so decide on case size first if you have a space constraint.

The CPU socket is stamped on the motherboard spec sheet. Current Intel boards use LGA1700 or LGA1851. Current AMD boards use AM5. Older boards use different sockets, so a 2020 motherboard will not accept a 2024 CPU. Check the socket before you buy anything else.

The CPU and Cooling System

The CPU (processor) is a small chip that does all the calculations. It plugs into the motherboard socket and generates heat proportional to its power output, measured in watts. A budget CPU might use 65 watts; a high-end one might use 250 watts. The hotter the CPU, the larger the cooler you need.

Cooling systems come in two types: air coolers and liquid coolers. Air coolers are metal heatsinks with fans; they are cheaper, simpler, and sufficient for most builds. Liquid coolers pump cool liquid through tubes to absorb heat more efficiently, which lets you run hotter CPUs or keep temperatures lower in a small case. Both types must match your CPU socket and fit inside your case.

When you buy a cooler, check that it lists your CPU socket on the box or product page. A cooler rated for LGA1700 will not mount on an AM5 socket. Also check the height: if your cooler is 160 millimeters tall and your case only clears 150 millimeters, it will not fit. Most cases list their maximum cooler height in the specs.

RAM and Storage: Memory vs. Permanent Space

RAM (random-access memory) is fast temporary memory that your CPU uses while programs are running. When you shut down the PC, RAM clears completely. Storage is permanent space where your operating system, programs, and files live. They are not interchangeable.

RAM comes in sticks that slot vertically into the motherboard. Most modern boards use DDR5 or DDR4 RAM, and the motherboard manual will tell you which. A typical build uses 16 gigabytes (two 8 GB sticks), though 32 GB is common for video editing or 3D work. RAM speed is measured in megahertz (MHz); faster RAM costs more but the real-world difference is small for most uses. Buy the speed your motherboard supports—the manual lists it.

Storage comes as a solid-state drive (SSD) or a hard disk drive (HDD). SSDs are faster and more reliable; they connect via M.2 slot (a small rectangular slot on the motherboard) or 2.5-inch SATA connector. HDDs are slower and cheaper; they use SATA connectors. A typical build has one 500 GB to 1 TB SSD for the operating system and programs, and optionally a larger HDD for file storage. You can add more drives later.

The Power Supply

The power supply converts wall electricity into the right voltage and current for your components. It has a large connector for the motherboard, a smaller connector for the CPU, and connectors for storage drives and the graphics card (if you have one). The power supply must have enough wattage to run everything at once, plus a safety margin.

To calculate wattage, add the power draw of your CPU and GPU (if you have one), then add 20 percent. A CPU that uses 125 watts plus a GPU that uses 300 watts equals 425 watts; add 20 percent and you need at least a 510-watt supply. A budget build with no GPU might need only 450 watts. Do not buy a power supply that is exactly your calculated wattage—the 20 percent margin matters.

Buy a power supply rated 80+ Bronze or better. This rating means the supply wastes less electricity as heat and is more reliable. Avoid unbranded or very cheap supplies; they fail more often and can damage your components. Reputable brands include Corsair, EVGA, Seasonic, and Be Quiet.

The Case

The case is a metal box that holds your motherboard, power supply, storage drives, and cooling system. It provides structure, airflow, and cable management. When you pick a case, check three things: the motherboard form factor it supports, the maximum cooler height it allows, and whether it has room for your storage drives.

Cases are sized to match motherboard sizes. An ATX case fits ATX, Micro-ATX, and Mini-ITX boards (with some wasted space for smaller boards). A Micro-ATX case fits Micro-ATX and Mini-ITX boards but not full ATX. A Mini-ITX case fits only Mini-ITX boards. Check the case manual or product page for the exact list.

Airflow matters for cooling. Cases with more fans and better ventilation run cooler. Budget cases often have one or two fans; better cases have three or more. You can add fans later, but it is easier to buy a case with good airflow from the start. Look for cases with mesh front panels and rear exhaust fans.

Optional Components: Graphics Cards and Extras

A graphics card (GPU) is optional if you only use your PC for web browsing, email, and office work. The CPU has built-in graphics that handle these tasks. If you play games, edit video, or do 3D work, you need a dedicated graphics card. The card plugs into a long slot on the motherboard and draws power from the power supply.

Other optional parts include extra case fans (for better cooling), a wireless network card (if your motherboard does not have built-in WiFi), and an SSD expansion card for faster storage. None of these are necessary for a working PC, but they improve performance or convenience depending on your use.

Putting It Together: The Order That Matters

Build in this order to avoid mistakes. First, install the CPU and cooler on the motherboard before putting the motherboard in the case—it is easier to work on a flat surface. Second, install RAM into the motherboard. Third, install the motherboard and power supply into the case. Fourth, connect the power cables from the supply to the motherboard and CPU. Fifth, install storage drives and connect them to power and the motherboard. Sixth, install the graphics card if you have one. Finally, connect the front panel connectors (power button, reset button, LED lights) to the motherboard.

Take your time and check each connection twice. Most mistakes are loose power connectors or RAM that is not fully seated. If the PC does not start, the first thing to check is whether the power supply switch is on—it is a small switch on the back of the power supply itself.

Frequently Asked Questions

Do I need a graphics card?

No, unless you game or do video editing. Most modern CPUs have built-in graphics that work fine for web browsing, email, and office work. A graphics card is only necessary if you need more graphics performance than the CPU can provide.

How much RAM do I actually need?

Sixteen gigabytes is the standard for most uses. Eight gigabytes is the minimum for comfortable web browsing and office work. Thirty-two gigabytes is useful if you edit video, work with large files, or run many programs at once. You can add more RAM later if you need it.

Can I use an old power supply from another PC?

Only if it has enough wattage and the right connectors. Check the wattage on the label and make sure it has a 24-pin motherboard connector and an 8-pin CPU connector. Old supplies may not have enough power for modern CPUs and GPUs.

What if my cooler does not fit in my case?

Return the cooler and buy a shorter one, or buy a larger case. Check the maximum cooler height in your case manual before you buy a cooler. This is why reading specs before purchasing matters.

Do all the cables come with the parts?

Power cables come with the power supply. Data cables for storage drives usually come with the motherboard. The case provides front panel connectors. You should not need to buy cables separately unless you are adding extra drives or fans later.