Check your CPU temperature right now
Your CPU is overheating if it's running above 80°C (176°F) under normal use, or above 90°C (194°F) even under heavy load like gaming or video editing. The easiest way to check is to download a free temperature monitor and look at the number it shows you.
Download HWiNFO (Windows) or Macs Fan Control (Mac). Install it, open it, and look for the line that says "CPU Package" or "Core Temp". That number is your current temperature. If you see a number above 80°C while you're just browsing or working in documents, your CPU is running too hot.
Write down the temperature you see. You'll need it to figure out what's actually wrong. If your CPU is at 45°C right now, you don't have an overheating problem — you have a different problem, and the rest of this guide will help you rule out what it isn't.
Key Takeaways
- Download HWiNFO or Macs Fan Control to see your actual CPU temperature in one number, measured in degrees Celsius.
- Temperatures above 80°C during normal use or above 90°C during heavy use mean your CPU is overheating and needs attention.
- The most common causes are dust blocking airflow, a loose or dried-out cooler, or a room that is simply too warm.
- Cleaning dust from your heatsink and fans is the first step and solves the problem in most cases.
- If cleaning doesn't work, your cooler may need reseating or the thermal paste may need replacing.
What causes a CPU to overheat
A CPU overheats when heat cannot escape from the processor fast enough. This happens for three main reasons: the cooler is not making good contact with the CPU, airflow inside your case is blocked, or your room is too warm for the cooler to work properly.
Dust is the most common culprit. Over months, dust builds up on your heatsink fins and fans, creating an insulating blanket that traps heat. A loose cooler — one that has shifted or was never seated properly — creates an air gap between the cooler and the CPU, and heat cannot jump that gap. Dried thermal paste, the gray compound between the cooler and CPU, has the same effect.
Less common but real: your case fans are not running, your room temperature is above 25°C (77°F), or you have too many components crammed into a small case with nowhere for hot air to escape. If you've just started overheating after months of normal operation, dust or a loose cooler is almost certainly the cause.
Clean dust from your heatsink and fans first
Shut down your computer completely and unplug it from the wall. Wait five minutes for it to cool. Open your case — usually four screws on the side panel — and look at the large metal fins attached to your CPU. That's your heatsink. Look for dust caked on those fins or on the fan blades next to them.
Use a can of compressed air to blow dust out of the heatsink fins. Hold the can upright and use short bursts. Blow from the inside of the case outward, pushing dust away from the fins rather than deeper into them. Do the same for any case fans you can see — the fans mounted on the front, back, or top of your case.
Do not touch the heatsink fins with your bare hands or a brush. They are thin and sharp, and you can bend them and make the problem worse. Compressed air is the right tool. After you've blown out the dust, close your case, plug in your computer, and turn it back on. Check the temperature again with HWiNFO or Macs Fan Control. If the temperature dropped by 10°C or more, dust was your problem and you're done.
Reseat your cooler if cleaning didn't help
If the temperature is still high after cleaning, your cooler may have shifted or lost contact with the CPU. Reseating means removing the cooler, cleaning off the old thermal paste, applying new paste, and reinstalling the cooler properly.
Shut down and unplug again. Remove the cooler by unclipping or unscrewing it — the method depends on your cooler type, so look at the cooler itself for clips or screws. Once it's off, you'll see the CPU underneath and the old thermal paste on top of it. Use a coffee filter or lint-free cloth with a small amount of rubbing alcohol to wipe away all the old paste until the CPU surface is clean and shiny.
Buy a small tube of thermal paste — Arctic MX-6 or Thermal Grizzly Kryonaut are common choices and cost $5 to $15. Apply a pea-sized dot in the center of the CPU. Reinstall the cooler, making sure it sits flat and all clips or screws are tight. The paste will spread when you clamp the cooler down. Turn the computer back on and check the temperature after 10 minutes of running.
Check that your case fans are running
While your case is open, look at the fans mounted on the front, back, or top. Spin them gently with your finger — they should spin freely. When you power on your computer, watch them for 30 seconds. They should be turning. If a fan is not spinning, it's dead and needs to be replaced.
A case with no airflow is like a closed box — hot air builds up inside and has nowhere to go. Even if your CPU cooler is working perfectly, the hot air it pushes out of the heatsink will just recirculate and heat up the CPU again. A single dead fan can cause overheating even when the cooler itself is fine.
If a fan is not spinning, you can replace it with a new one of the same size — measure the fan in millimeters, usually 80mm, 92mm, or 120mm. A replacement fan costs $10 to $30 and takes five minutes to install. Unplug the old fan's power cable from the motherboard, unscrew it, and screw in the new one in the same orientation.
Lower your room temperature or improve case airflow
If your room is very warm — above 25°C (77°F) — your cooler has less temperature difference to work with. A cooler works by moving heat from the CPU to the air around it. If the air is already hot, the cooler cannot move heat as efficiently. If you live in a hot climate or your room gets direct sunlight, this can be a real limit.
The simplest fix is to improve airflow in your case. Make sure your case has at least one fan pulling air in from the front and one fan pushing air out the back. If you only have one fan, add a second one. Make sure nothing is blocking the front of your case — move it away from walls or enclosed spaces where hot air can recirculate.
If your room temperature is the problem, you may need to run your computer in a cooler room, use air conditioning, or accept that your CPU will run warmer in summer. This is normal and not dangerous as long as temperatures stay below 95°C.
When to replace your cooler entirely
If you've cleaned the dust, reseated the cooler with fresh thermal paste, confirmed your case fans are running, and your CPU is still above 80°C during normal use, your cooler may be failing. Coolers wear out over time, especially liquid coolers, which can develop leaks or pump failures.
A replacement air cooler costs $30 to $60 and takes 15 minutes to install. A liquid cooler costs $80 to $200. Before you buy, check what socket your CPU uses — look up your CPU model and find the socket type (like LGA1700 for Intel or AM5 for AMD). Make sure the new cooler supports that socket.
Installation is the same as reseating: remove the old cooler, clean off the paste, apply new paste to the CPU, and install the new cooler. If you're not comfortable doing this yourself, a local computer repair shop can do it for $50 to $100 in labor.
Frequently Asked Questions
What temperature is too hot for a CPU?
Above 80°C during normal use or above 90°C during heavy gaming or video editing means your CPU is overheating. Most CPUs can handle up to 95°C before they start to throttle — slow themselves down to reduce heat. Sustained temperatures above 95°C can shorten your CPU's lifespan.
Can overheating damage my CPU permanently?
Yes, but it takes sustained high temperatures over months or years. A single day of running at 95°C will not damage your CPU. Repeated thermal cycling — heating and cooling — can degrade the solder connections inside the chip over time. The sooner you fix overheating, the better.
Is 70°C normal for a CPU?
Yes. 70°C during heavy use like gaming is normal and healthy. 70°C during light browsing or document work is slightly warm but not dangerous. Anything under 80°C during normal use is fine and does not need attention.
Do I need to replace my thermal paste every year?
No. Thermal paste lasts three to five years under normal conditions. You only need to replace it if you remove your cooler for cleaning or reseating, or if your CPU temperature suddenly jumps after months of normal operation — a sign the paste has dried out.
Can I use a hair dryer to blow dust out instead of compressed air?
No. A hair dryer creates static electricity, which can damage your motherboard and CPU. Compressed air is safe because it's inert. If you don't have compressed air, use a soft brush designed for electronics, or take your computer to a repair shop for cleaning.