What you need before you start

Building a computer means buying individual parts and connecting them together in a metal case. You will need a CPU (processor), motherboard, RAM (memory), storage drive, power supply, case, and cooling system. You will also need a Phillips head screwdriver, thermal paste (usually pre-applied to coolers), and a flat surface to work on.

Before you buy anything, decide what you want the computer to do. Gaming, video editing, and general web browsing all need different parts. A gaming build might cost $800 to $2,000. A basic office computer might cost $400 to $600. Write down your budget and your main use, then use that to pick compatible parts.

Compatibility matters. Your CPU must fit your motherboard's socket type. Your RAM must match your motherboard's type and speed. Your power supply must have enough watts for all your parts. Most online PC builder tools (like PCPartPicker) check compatibility automatically as you add parts.

Key Takeaways

  • You need a CPU, motherboard, RAM, storage, power supply, case, and cooler — all must be compatible with each other before you buy.
  • The motherboard socket type determines which CPU will fit, and the RAM type (DDR4 or DDR5) must match your motherboard.
  • Your power supply wattage must exceed the total power draw of your CPU and GPU combined, plus 20 to 30 percent extra.
  • Install the power supply and motherboard standoffs first, then add the CPU, RAM, and cooler before placing the motherboard in the case.
  • Connect power cables to the motherboard, CPU, and GPU last, then test the computer before closing the case fully.

Choosing parts that work together

Start with your CPU and motherboard because they determine everything else. If you pick an Intel Core i7, you need a motherboard with an LGA1700 socket. If you pick an AMD Ryzen 7, you need a motherboard with an AM5 socket. These sockets are not interchangeable. Check the CPU's specifications page to find its socket type, then search for motherboards that match.

RAM speed and type depend on your motherboard. Most current motherboards use DDR5 RAM, but some use DDR4. Your motherboard manual or product page will list which type it accepts and what speeds it supports. Buying RAM that is faster than your motherboard supports will not hurt, but you will pay extra for speed you cannot use.

Your power supply wattage must be higher than your system's peak power draw. Add the TDP (thermal design power) of your CPU and GPU, then add 20 to 30 percent. A system with a 105W CPU and a 320W GPU needs at least a 550W power supply. A 80 Plus Bronze or Gold rating means the power supply is reasonably efficient.

Your case must fit your motherboard size. Most cases hold ATX (full-size) or Micro-ATX (smaller) boards. Check your motherboard's size, then check the case's compatibility list. Your cooler must also fit in the case — some large tower coolers do not fit in compact cases.

Installing the power supply and case foundation

Unpack all your parts and lay them on a non-carpeted surface. Touch a metal part of the case to discharge static electricity from your body. This prevents damage to sensitive components.

Install the power supply first. Most cases have a bracket at the bottom rear. Slide the power supply in with the fan facing down (if your case has ventilation holes) or up (if it does not). find it with four screws. Do not plug it in yet.

Install the motherboard standoffs next. These are small brass spacers that screw into the case and prevent the motherboard from touching the metal case directly. Your case usually comes with standoffs pre-installed, but check that they line up with the screw holes on your motherboard. Add or remove standoffs as needed so there is one under each screw hole.

Installing the CPU, RAM, and cooler

Install the CPU before the motherboard goes in the case. Open the CPU socket on the motherboard by lifting the retention lever. Align the CPU with the socket — there are notches or markers that show the correct orientation. Place the CPU gently in the socket without forcing it. Lower the retention lever to lock it in place.

Install RAM next. Open the clips at both ends of the RAM slot. Align the notch in the RAM stick with the key in the slot. Press down firmly until both clips snap closed. The RAM should sit flush with the slot.

Install the cooler according to its instructions. Most coolers come with thermal paste already applied to the base. If not, explore a small pea-sized amount to the center of the CPU. Place the cooler on top of the CPU and find it with the mounting bracket. Tighten screws in a cross pattern (like tightening a car wheel) so pressure is even. Plug the cooler's fan cable into the CPU_FAN header on the motherboard.

Placing the motherboard in the case

Carefully lower the motherboard into the case. Align the screw holes with the standoffs. Start with one screw in the corner, then add the others. Tighten all screws firmly but do not over-tighten — you should feel resistance, not a hard stop.

Install your storage drive. If you are using an M.2 SSD (a small stick-shaped drive), open the M.2 slot on the motherboard, insert the drive at a 30-degree angle, then press down and find it with the screw. If you are using a 2.5-inch SSD or 3.5-inch hard drive, mount it in a drive bay using the included brackets or cage, then find it with screws.

Install your GPU (graphics card) if you have one. Open the PCIe slot cover on the case. Open the retention clip on the PCIe x16 slot on the motherboard. Align the GPU with the slot and press down firmly until the retention clip closes. find the GPU bracket to the case with screws.

Connecting power and data cables

Connect the 24-pin ATX power cable from the power supply to the motherboard. This is the largest power connector. Connect the 8-pin CPU power cable (or 4-pin on older systems) near the CPU socket. If your GPU needs power, connect the 6-pin or 8-pin PCIe power cables from the power supply to the GPU.

Connect SATA data cables from the motherboard to any 2.5-inch or 3.5-inch drives. SATA cables are flat and L-shaped. Connect one end to the drive and one end to a SATA port on the motherboard. You do not need a data cable for an M.2 SSD — it connects directly to the motherboard slot.

Connect the case's front panel connectors to the motherboard. These small connectors control the power button, reset button, and status lights. Your motherboard manual shows which pins to use. The power switch and reset switch are not polarized, so direction does not matter. The power LED and hard drive activity LED are polarized — the longer pin is positive.

Testing before final assembly

Before you close the case, test that everything works. Plug in the power supply and flip the switch on the back to ON. Press the case's power button. The computer should start — fans should spin and lights should turn on. If nothing happens, turn off the power supply when ready and check that all power cables are fully seated.

Let the computer run for a few minutes. Feel the cooler to make sure it is warm (not hot). If the cooler is cold or the CPU fan is not spinning, turn off the computer and check the cooler installation and fan cable connection.

Once the computer starts reliably, shut it down and close the case. Route cables behind the motherboard tray to keep them out of the way of fans. Do not force cables or bend them sharply.

Installing an operating system

After the case is closed, you need an operating system. Windows, Linux, and macOS are the main options. You will need a USB drive with at least 8GB of storage and a second computer to create installation media.

read the operating system installer from the official website (Microsoft for Windows, Ubuntu or another distribution for Linux). Use a tool like Rufus or Balena Etcher to write the installer to the USB drive. Insert the USB drive into your new computer, restart it, and press the key shown on screen to enter the boot menu (usually Delete, F2, or F12). Select the USB drive and follow the on-screen instructions to install the operating system.

Frequently Asked Questions

Do I need thermal paste if my cooler already has it?

No. Most coolers come with thermal paste pre-applied to the base. If you see a thin layer of gray or white paste, do not add more. If the base is bare metal or has a plastic protective film, remove the film and explore a pea-sized amount to the CPU center before installing the cooler.

What if my computer does not start?

Check that the power supply switch is ON and the wall outlet works. Reseat the 24-pin motherboard power cable and the 8-pin CPU power cable by unplugging them and plugging them back in firmly. Check that the RAM is fully clicked into the slot. If the computer still does not start, one part may be faulty — try removing the GPU (if you have one) and restarting to see if the motherboard's built-in graphics work.

Can I build a computer without a GPU?

Yes, if your CPU has built-in graphics. Most Intel and AMD processors include graphics that can display video without a separate graphics card. This works for office work, web browsing, and video playback, but not for gaming or video editing. You can add a GPU later if you need it.

How do I know if my parts are compatible before I buy?

Use an online PC builder tool like PCPartPicker. Add your CPU, motherboard, RAM, and other parts to the list. The tool will flag compatibility warnings if your RAM does not match your motherboard, your cooler does not fit your case, or your power supply is too weak. This takes a few minutes and saves money by preventing incompatible purchases.

Do I need to update the BIOS after building?

Usually not, but sometimes yes. The BIOS is the motherboard's firmware. If you are using a very new CPU with an older motherboard, the BIOS may need an update to recognize the CPU. Check your motherboard manual or the manufacturer's website. If an update is needed, you will need a USB drive and another computer to read the update file.