Applying thermal paste correctly is one of those small jobs that makes a big difference to how your PC runs. Whether you’re building a new system, replacing an old CPU cooler, or reseating a heatsink after a clean, this guide walks you through the process from start to finish so your processor stays cool and stable.

Thermal paste, also called thermal compound or thermal interface material, fills the tiny gaps between the surface of your CPU and the base of the cooler. Without it, air pockets trap heat and your processor can run hotter than it should, sometimes hot enough to trigger throttling. Getting the application right is not complicated, but a few small mistakes can lead to uneven cooling or a messy cleanup later.

What you’ll need

  • A tube of thermal paste (avoid using paste that has dried out or separated)
  • Isopropyl alcohol (90 percent or higher works best)
  • Lint-free cloths or coffee filter paper
  • A plastic spreader or an old card, if you prefer to spread the paste manually
  • Your CPU cooler and any mounting hardware that came with it

Prepare the CPU and cooler

  1. Power off and unplug your PC, then open the case and locate the CPU socket. If you’re fitting a processor for the first time, follow the steps for installing a CPU in your gaming PC before you move on to the paste.
  2. If there’s old thermal paste on the CPU or cooler, dampen a lint-free cloth with isopropyl alcohol and gently wipe both surfaces clean. Let them dry fully before continuing, since any leftover moisture or residue can affect contact.
  3. Check that the cooler’s base plate is clean and free of dust, hair, or old paste residue. A dirty base plate will not sit flush against the CPU no matter how carefully you apply the paste.

Apply the thermal paste

  1. Place a small amount of paste in the centre of the CPU’s integrated heat spreader. A dot roughly the size of a grain of rice or a small pea is usually enough for most consumer CPUs. Using too much paste can cause it to squeeze out the sides once the cooler is mounted, while too little leaves gaps that trap heat.
  2. For larger CPUs, or coolers with an uneven base, some builders prefer a thin line down the middle instead of a single dot, since it spreads more evenly under pressure.
  3. Avoid spreading the paste yourself unless your cooler has an unusual shape or a particularly large contact surface. In most cases, the pressure from mounting the cooler will spread the paste evenly across the surface on its own.
  4. Lower the cooler straight down onto the CPU without twisting or sliding it side to side. Twisting can push paste unevenly or trap air bubbles under the base plate.

Mount the cooler

  1. Secure the cooler using its mounting brackets or screws, following the tightening pattern recommended by the manufacturer. Most coolers need a diagonal or star pattern to apply even pressure across the CPU.
  2. Tighten screws gradually and evenly rather than fully tightening one side before moving to the next. This helps the base plate sit flat and spreads the paste consistently.
  3. Reconnect the cooler’s fan cable to the correct header on the motherboard, then close up the case and reconnect power.
  4. Boot the system and check temperatures using your motherboard’s monitoring software or a third-party tool. Idle temperatures in the 30 to 45 degree Celsius range are typical for most modern CPUs, though this varies by chip and ambient temperature.

Tips and troubleshooting

  • If temperatures seem unusually high after installation, remove the cooler, check the paste spread, and reapply if it looks patchy or concentrated on one side.
  • Never reuse old, dried-out thermal paste. If it has become crumbly or separated into a liquid and solid layer, replace it with a fresh tube.
  • Check that the cooler is making full contact with the CPU. A tilted or poorly seated cooler is a common cause of uneven temperatures even when the paste application is done correctly.
  • If you’re reseating a cooler you’ve used before, always clean off the old paste first rather than applying new paste on top of it.
  • Refer to Intel’s official cooler installation guidance or AMD’s official support resources if you’re unsure about mounting pressure or bracket compatibility for your specific CPU and cooler combination.

Frequently asked questions

How much thermal paste should you use?

A dot around the size of a grain of rice or a small pea is enough for most CPUs. The pressure from mounting the cooler spreads it across the surface, so more paste is not necessarily better and can lead to overflow around the edges.

How often should you replace thermal paste?

Many builders replace thermal paste every two to three years, or whenever they remove the cooler for maintenance or an upgrade. Paste can dry out over time, which reduces its effectiveness at transferring heat.

Can you use too little thermal paste?

Yes. Too little paste leaves gaps between the CPU and cooler that trap heat instead of transferring it away, which can cause higher idle and load temperatures than expected.

Do you need to spread the paste manually?

Usually not. For most standard CPUs and coolers, a single dot in the centre spreads evenly once the cooler is mounted and tightened. Manual spreading is generally only needed for larger or irregularly shaped contact surfaces.