Thermal paste goes between your processor and its cooler to fill microscopic gaps and transfer heat away from the chip

Thermal paste (also called thermal compound or TIM — thermal interface material) is a thick, putty-like substance that sits in the tiny space between your CPU and the metal base of your cooler. Even though both surfaces look smooth to the naked eye, they have microscopic peaks and valleys. Thermal paste fills those gaps so heat can move efficiently from the processor into the cooler, where a fan can carry it away. Without it, your CPU will overheat within seconds of turning on.

The paste itself does not conduct heat as well as direct metal-to-metal contact would, but it conducts far better than air does. Most thermal pastes are good enough that the difference between brands matters less than applying the right amount in the right way. Too much paste can actually insulate the CPU and make temperatures worse. Too little leaves air gaps that trap heat.

Key Takeaways

  • Clean the old paste off both the CPU and cooler base with isopropyl alcohol and a lint-free cloth before applying new paste.
  • A rice-grain or pea-sized amount in the center of the CPU is the standard method that works for most processors and coolers.
  • Spread the paste only if your cooler's instructions specifically tell you to; most modern coolers spread it themselves when you clamp them down.
  • Let the paste cure for a few hours before pushing the system hard, because fresh paste has lower thermal conductivity until it settles.
  • Reapply thermal paste every two to three years, or whenever you remove and reinstall your cooler.

What you need before you start

Gather these items before you open your computer: thermal paste (Arctic MX-6, Noctua NT-H2, and Thermal Grizzly Kryonaut are common choices that perform similarly), isopropyl alcohol (90% or higher concentration), a lint-free cloth or coffee filter, and a plastic spreader tool (many thermal paste tubes include one, or you can use a plastic card). You will also need a Phillips screwdriver to remove your cooler.

Power off your computer completely and unplug it from the wall. Wait at least five minutes for the CPU to cool. If you have been running the system, the cooler and paste will be hot enough to burn your skin. Open your case and locate the CPU cooler — it is the large metal or plastic assembly sitting directly on top of your processor.

Removing the old cooler and cleaning the surfaces

The removal process depends on your cooler type. Most tower coolers have two or four screws holding the mounting bracket to the motherboard; remove these screws and gently lift the cooler straight up. Some coolers have a lever or latch instead of screws — flip or slide it to release the cooler. Intel stock coolers (the ones that come with the processor) usually have a push-pin clip on each corner; push each pin from underneath to release them, then lift the cooler away.

Once the cooler is off, you will see old thermal paste on both the CPU surface and the flat metal base of the cooler. This paste is usually gray or white and may be dried out or still slightly tacky. Dampen your lint-free cloth with isopropyl alcohol and wipe the CPU surface in circular motions until all visible paste is gone. Repeat on the cooler base. Use a fresh section of cloth for each surface so you do not transfer old paste back onto the CPU. Let both surfaces air-dry for a minute — isopropyl alcohol evaporates quickly.

Applying the paste: the rice-grain method

The rice-grain method is the most reliable approach for most CPUs and coolers. Squeeze a small amount of thermal paste onto the center of the CPU — roughly the size of a grain of rice or a small pea. This is typically a line about 3 to 5 millimeters long, or a dot about the size of a lentil. If you are unsure, start smaller; you can always add more, but removing excess is messy.

Do not spread the paste yourself unless your cooler's manual specifically instructs you to. Modern coolers — both air and liquid — are designed to spread the paste evenly when you clamp them down. The pressure from mounting the cooler distributes the paste across the entire CPU surface. Spreading it by hand before mounting often creates uneven coverage and air pockets.

If your cooler manual does say to spread the paste, use the plastic spreader tool or a plastic card held at a shallow angle. Drag it across the CPU surface in one direction only, applying light pressure. Do not scrape back and forth, which traps air bubbles. A thin, even layer is the goal.

Reinstalling the cooler and securing it properly

Align the cooler base with the CPU and mounting bracket. For tower coolers, insert the screws and tighten them in an X pattern — if there are four screws at the corners, tighten top-left, then bottom-right, then top-right, then bottom-left. This ensures even pressure across the CPU. Tighten each screw firmly but do not overtighten; you should feel resistance, not a hard stop. Overtightening can crack the CPU or motherboard.

For coolers with levers or latches, push or flip them until you hear or feel a click. For Intel stock coolers, push each pin from underneath until it clicks into place. The cooler should sit flat against the CPU with no rocking or gaps. If it rocks, remove it, clean the surfaces again, and reapply paste — something is preventing full contact.

Reconnect the cooler's fan cable to the CPU fan header on your motherboard. This is usually a three-pin or four-pin connector near the CPU socket. Push it straight down until it clicks.

Testing and what to expect in the first hours

Close your case, plug in the power cable, and turn on your computer. Enter your BIOS (usually by pressing Delete, F2, or F12 during startup — your motherboard manual will say which key) and check the CPU temperature. It should be between 30 and 50 degrees Celsius at idle, depending on your room temperature and cooler quality. If the temperature is above 80 degrees Celsius at idle, power off immediately, remove the cooler, and check that it is making full contact with the CPU.

Fresh thermal paste has lower thermal conductivity than paste that has cured for a few hours. You may see temperatures drop by 5 to 10 degrees Celsius over the first two to four hours of use. Avoid running heavy workloads (gaming, video rendering, stress tests) for at least the first hour. Light use like web browsing and document editing is fine.

When to reapply thermal paste

Thermal paste does not need to be replaced just because it is old. It degrades over time — typically two to three years — as the carrier fluid evaporates and the paste hardens. If your CPU temperatures are creeping upward over months or years, and your cooler fan is clean, old paste is often the cause. Reapply it the same way you did the first time.

You must reapply paste whenever you remove and reinstall your cooler, even if the old paste looks fine. Removing the cooler breaks the seal and creates air pockets. Reusing the old paste in this situation usually results in higher temperatures.

Frequently Asked Questions

How much thermal paste should I use?

A rice-grain or pea-sized amount in the center of the CPU is the standard. This is roughly 3 to 5 millimeters long if you squeeze a line, or about the size of a lentil if you use a dot. More paste does not cool better — it actually insulates the CPU and raises temperatures.

Can I use thermal paste from a tube that is several years old?

Yes, if the paste has not dried out completely. Squeeze a small amount onto a surface and check the consistency. If it is still creamy and not hard or separated into liquid and powder, it should work. If it is rock-hard or has obvious separation, buy new paste.

What if my CPU temperature is still too high after reapplying paste?

Check that your cooler is mounted flat and making full contact with the CPU. Remove the cooler, clean both surfaces with isopropyl alcohol, and reapply paste. If temperatures are still high, your cooler may be failing or your case may have poor airflow. Make sure case fans are spinning and intake vents are not blocked by dust.

Do I need to remove thermal paste before selling or giving away my computer?

No, but many people do for cleanliness. If you are keeping the cooler on the CPU, you can leave the paste as is. If you are removing the cooler to reuse it elsewhere, clean off the old paste with isopropyl alcohol so the cooler base is bare metal.

Is one brand of thermal paste significantly better than others?

Most mainstream thermal pastes perform within a few degrees of each other. Arctic MX-6, Noctua NT-H2, and Thermal Grizzly Kryonaut are all solid choices. The application method and cooler quality matter more than the brand. Avoid extremely cheap pastes from unknown sellers, as they may separate or dry out quickly.