Thermal grease goes between your processor and its cooler to fill the microscopic gaps that air cannot

Thermal grease (also called thermal paste or thermal compound) is a sticky substance that conducts heat better than air. Your CPU or GPU and its cooler look flat to the naked eye, but under magnification both surfaces are rough with tiny peaks and valleys. When you clamp a cooler directly onto a processor, air pockets form in those valleys. Thermal grease fills those gaps so heat can flow from the chip to the cooler instead of getting trapped.

Without thermal grease, your processor will overheat in seconds and shut itself down to avoid damage. Applying it correctly means using the right amount in the right spot — too little leaves air gaps, too much wastes material and can squeeze out onto the motherboard, and applying it to the wrong area wastes both.

This guide covers the standard method for desktop CPUs and GPUs. Laptop thermal paste application is different and usually requires disassembling the entire machine, so check your laptop's service manual before attempting it.

Key Takeaways

  • Thermal grease must be applied between a processor and its cooler, not on top of the cooler itself or anywhere else on the motherboard.
  • A rice-grain-sized amount in the center of the processor is the standard method that works for most CPUs and GPUs.
  • The cooler's weight will spread the grease evenly when you clamp it down — you do not need to spread it yourself with a tool.
  • Remove old thermal grease completely with isopropyl alcohol before applying new grease, or the old and new layers will not conduct heat properly.
  • Most thermal grease dries out or degrades over three to five years, so reapplying it can lower temperatures if your machine has been running for that long.

What you need before you start

Gather these items before you open your machine: thermal grease (any brand rated for CPUs or GPUs will work — Arctic MX-6, Thermal Grizzly Kryonaut, and Noctua NT-H2 are common choices), isopropyl alcohol (90% or higher concentration), lint-free wipes or coffee filters, and a plastic scraper or old credit card. Do not use paper towels, which leave fibers behind.

You will also need access to your cooler's mounting hardware. For Intel CPUs, this is usually the backplate and retention bracket that came with your cooler. For AMD CPUs, the cooler mounts directly to the socket. For GPUs, the cooler is usually bolted to the card itself. Check your cooler's manual to see what tools you need — most use Phillips head screwdrivers, but some require a wrench or hex key.

Power off your machine completely and unplug it from the wall. Wait at least 15 minutes for the processor to cool. If you are replacing old thermal grease, the processor should be cool enough to touch comfortably on the back of your hand.

Removing the old cooler and cleaning the processor

Locate the mounting bolts or clips that hold your cooler in place. For most tower coolers on Intel systems, there are four bolts around the edges of the cooler base. For AMD systems, there is usually a single lever or clip on one side of the socket. For GPU coolers, bolts are typically on the back of the card. Loosen these fasteners in a cross pattern (opposite corners first, then the other two) so pressure releases evenly. Do not remove them all at once, or the cooler may tilt and damage the processor.

Once the cooler is loose, lift it straight up and away from the processor. Do not twist or rock it side to side — you may bend the processor's pins (on Intel) or damage the socket (on AMD). Set the cooler aside on a clean surface.

You will now see the processor's surface covered with old thermal grease. Dampen a lint-free wipe with isopropyl alcohol and wipe the entire surface in one direction until no grease remains. Use a plastic scraper to remove stubborn buildup, then wipe again with a fresh alcohol-dampened wipe. The surface should look shiny and clean, with no visible residue. Let the alcohol evaporate completely — this usually takes two to three minutes.

Applying thermal grease to the processor

Place a single rice-grain-sized amount of thermal grease in the center of the processor. This is roughly the size of a grain of uncooked rice — about 3 to 4 millimeters across. If you are unsure, start with less rather than more. You can always add more, but removing excess is messy.

Do not spread the grease across the processor's surface yourself. The weight of the cooler will spread it evenly when you clamp it down. Spreading it by hand often creates air bubbles and uneven coverage, which actually reduces heat transfer. The only exception is if you are using a very thick thermal grease that does not spread easily — in that case, use a plastic spreader or old credit card to create a thin, even layer, but this is rarely necessary with modern thermal compounds.

Some people apply a tiny amount to the cooler's base plate as well, especially if the base plate is not perfectly flat. This is optional and not required for most coolers. If you do this, use an even smaller amount — a few grains of rice total — and spread it very thinly across the entire base plate with a plastic tool.

Reinstalling the cooler and checking your work

Lower the cooler straight down onto the processor, keeping it level. Align the mounting holes with the bolts or clips on your motherboard or socket. Do not let the cooler tilt or shift as it descends, or you may wipe the thermal grease off the processor.

Tighten the mounting bolts in a cross pattern — if there are four bolts, tighten the top-left, then bottom-right, then top-right, then bottom-left. This ensures even pressure across the cooler base. Tighten each bolt only finger-tight at first, then go around again and tighten them fully. Do not over-tighten, which can crack the processor or warp the cooler base. The bolts should be snug but not requiring excessive force.

Once the cooler is mounted, check that no thermal grease has squeezed out onto the motherboard or socket. A tiny amount around the edges is normal, but if grease has spread across the motherboard, use an alcohol-dampened wipe to clean it up. Grease on the motherboard does not conduct electricity, but it can trap dust and moisture, so keeping it clean is good practice.

Verifying temperatures after application

Plug your machine back in and power it on. Let it boot into your operating system and sit idle for five minutes. Then open a temperature monitoring tool to check your processor's temperature. On Windows, HWiNFO or Core Temp will show CPU temperatures. On Mac, Macs Fan Control shows CPU temperature. For GPUs, GPU-Z (Windows) or Macs Fan Control (Mac) will display GPU temperature.

Your processor's idle temperature should be 10 to 20 degrees Celsius above room temperature. If your room is 20°C, your CPU should idle around 30 to 40°C. If temperatures are significantly higher — say, 60°C or more at idle — the thermal grease may not have made good contact. Power off, let the machine cool, and check that the cooler is mounted evenly and the bolts are tight.

Run a stress test like Prime95 (CPU) or FurMark (GPU) for 10 to 15 minutes to see how temperatures behave under load. Your processor should not exceed 85°C during this test. If it does, the thermal grease application may need adjustment, or your cooler may not be adequate for your processor.

Common mistakes and how to avoid them

The most common mistake is applying too much thermal grease. More grease does not mean better cooling — it means grease will squeeze out onto the motherboard, and the excess layer actually insulates the processor instead of conducting heat. Start with a rice-grain amount and resist the urge to add more.

The second mistake is spreading the grease yourself before mounting the cooler. This creates air bubbles and uneven coverage. Let the cooler's weight do the spreading.

The third mistake is not cleaning old grease completely. If you leave a thin layer of old, dried grease underneath new grease, the two layers will not bond and heat will not transfer properly. Wipe until the surface is visibly clean and shiny.

The fourth mistake is tilting or twisting the cooler as you remove it or install it. This can wipe grease off the processor or bend processor pins. Always move the cooler straight up and straight down.

When to reapply thermal grease

Thermal grease degrades over time as it dries out and loses its ability to conduct heat. Most thermal compounds last three to five years before performance noticeably drops. If your machine is three or more years old and temperatures have crept up over time, reapplying thermal grease may lower temperatures by 5 to 15 degrees Celsius.

You should also reapply thermal grease if you remove and reinstall your cooler for any reason — cleaning, replacing a fan, or upgrading. Even if the old grease looks fine, removing the cooler breaks the seal and introduces air gaps. Always use fresh grease when you remount a cooler.

If your processor is brand new and you are installing it for the first time, some coolers come with thermal grease pre-applied to the base plate. Check your cooler's documentation. If grease is already applied, you do not need to add more — just mount the cooler as-is. If the cooler is bare, apply grease as described above.

Frequently Asked Questions

Can I use thermal grease on my laptop?

Laptop thermal paste application requires disassembling the entire machine down to the motherboard, which is beyond this guide. Consult your laptop's service manual or contact the manufacturer. Many laptops have warranty restrictions on opening the case yourself.

What if I applied too much thermal grease?

Power off your machine, let it cool, and remove the cooler. Wipe away the excess grease with isopropyl alcohol and a lint-free wipe. Clean the processor surface completely, then apply a fresh rice-grain amount and remount the cooler.

Does the brand of thermal grease matter?

Most modern thermal compounds perform similarly. Arctic MX-6, Thermal Grizzly Kryonaut, and Noctua NT-H2 are all reliable choices. Avoid extremely cheap or very old thermal grease, which may have degraded. For most users, any brand rated for CPUs or GPUs will work fine.

Why is my processor still running hot after reapplying thermal grease?

Check that the cooler is mounted evenly and all bolts are tight. Verify that your cooler's fans are spinning and not clogged with dust. If temperatures remain high, your cooler may be undersized for your processor, or your case may have poor airflow. Thermal grease alone cannot fix these problems.

Can I apply thermal grease to other parts of my motherboard?

No. Thermal grease should only go between a processor and its cooler. Applying it elsewhere serves no purpose and can trap dust or interfere with electrical connections. If grease accidentally gets on other parts, clean it off with isopropyl alcohol.