How to Apply Thermal Paste Correctly

Knowing how to apply thermal paste correctly is one of the easiest wins in PC building — a pea-sized dot in the middle, a cooler pressed down evenly, and your CPU can run several degrees cooler than with a bad application. It takes two minutes, it costs almost nothing, and it is the difference between a quiet PC and a hot one.

What thermal paste actually does

Thermal paste fills the tiny gaps between the CPU and the cooler. Both surfaces look flat, but at a microscopic level they are rough, and air trapped in those gaps is a bad conductor of heat. The paste replaces the air with a material that conducts heat well, so the heat flows from the chip into the cooler instead of staying in the chip. Our CPU cooling basics guide explains the rest of the cooling chain, and our how long a desktop CPU lasts guide explains why a cooler chip lasts longer.

How much paste to use

Use a pea-sized dot in the centre of the CPU — about the size of a grain of rice, or a small pea. That is enough: when you press the cooler down, the paste spreads across the whole surface. Too much paste squeezes out the sides and makes a mess; too little leaves dry patches that overheat. Do not spread it with a card or your finger — the pressure of the cooler does a better job than you can, and spreading it by hand traps air bubbles. Our how to choose the right CPU cooler guide covers the cooler itself, and the paste is the last step in the same job.

Step-by-step: applying thermal paste

First, clean the CPU and the cooler base — see the next section. Then put the pea-sized dot in the centre of the CPU. Then lower the cooler straight down, without sliding it around, and tighten the screws in a cross pattern, a little at a time, so the pressure is even. Finally, plug in the fan and check the temperature — our how to benchmark your CPU guide and our best CPU benchmark software guide show you how to measure it. A Ryzen 7 9700X with a good paste application should idle in the 30s and stay under 80°C under full load.

How to clean off old thermal paste

To remove old paste, use isopropyl alcohol (90% or higher) and a lint-free cloth or a coffee filter. Wipe gently until both surfaces are clean and shiny, and let the alcohol dry for a minute before you apply new paste. Do not use water, and do not scrape with anything hard — a scratched CPU surface is worse than old paste. This is also the moment to check the cooler: if the base is scratched or the fan is noisy, replace it — see our best CPU cooler for gaming guide.

How often should you replace thermal paste?

Replace the paste every two to three years, or whenever you remove the cooler for any reason. Paste dries out over time, and dry paste conducts heat badly — if your temperatures have crept up over the years, old paste is a likely cause. High-end paste lasts longer than cheap paste, but the difference is a few degrees at most, so do not spend a fortune on it. A 14900K that runs hot may benefit from fresh paste, but a Ryzen 7 7700X that runs cool probably does not need it yet.

Mistakes that make your CPU hotter

• Using too much paste — it squeezes out and makes a mess.
• Using too little paste — it leaves dry patches.
• Spreading it by hand — it traps air bubbles.
• Reusing old, dried-out paste.
• Tightening the cooler unevenly — one side presses harder than the other.

The bottom line

Thermal paste is simple: a pea-sized dot, a clean surface, and a cooler tightened evenly. Do that, and your CPU will run cooler, quieter and faster — see our CPU benchmarks explained guide for how temperature affects performance. Browse our cooling guides and our overclocking guides for the next steps.