Why should I stress test a CPU?

Stress testing a CPU means running it at maximum capacity for a sustained period of time in order to evaluate the stability of its performance. In this article, we’ll focus on the processor (CPU, or central processing unit) and stress test it using multiple techniques. We’ll also show you the best CPU stress-testing software, including for CPU load tests.

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    If you already know why you should stress test your CPU and simply want to figure out the best way to do so, skip down below to read about the best tools for stress testing your CPU.

    Stress testing your CPU with a frying pan, or the wrong way to stress test a CPU.Don’t try this at home. Surely there are better (and safer) ways to stress test your CPU than by putting it in a frying pan.

    Common reasons to stress test your CPU

    The best reasons to check the stability of your CPU when it’s pushed to its limits are:

    • You built a new computer. Congrats, you’ve just built your own PC. Your next step is to test whether the thermal paste and cooling systems all work hand-in-hand to handle stress.

      Putting thermal paste on your CPUApplying thermal paste to your CPU.

    • You bought a new PC or laptop. Just got a brand-new machine? Run it through some stress testing and see how it performs. This is especially important if you have a super-slim laptop with little to no cooling.

    • You have an old laptop or PC. If your computer is showing its age, perhaps by randomly shutting down, you’re likely wondering how you can revive your dying PC. A good first step is to run a stress test to see whether temperatures and high usage are an issue.

    • You’re overclocking. If you’re an enthusiast or gamer who wants to squeeze every ounce of performance out of your computer, stress testing is an essential part of this process. Learn more about how to safely overclock your PC.

    How long should I stress test a CPU?

    To ensure stability, you don’t need to stress test your processor for more than one hour — that’s plenty of time for your CPU to reach its maximum temperature. If you absolutely need to make sure everything is stable and working properly, let it run for 24 hours. But in reality, I’ve never needed such a prolonged test for any of the overclocks I’ve performed or the PCs I’ve built.

    Is stress testing safe?

    Unless you’re running these stress tests for a month, you’re probably fine. If your CPU hits its critical limits, the PC will shut down before any harm can be done. Only in very rare cases, and with much older CPUs, could you actually damage your hardware if you let it run for a prolonged period of time. And if that happens, it was bound to happen at some point anyways. 

    In most cases, you’re fine to run these tests. But beware that the excessive heat produced during the test will contribute to the gradual wear and tear of your PC. Always check your CPU temperature and avoid overheating.

    How does stress testing work?

    There are a lot of utilities out there that help with stress testing processors, but how do they actually “stress”? The stress comes from simulating a full processing load.

    For example, Prime95 — one of the most popular stress testing programs — uses the search for Mersenne prime numbers. This causes CPUs to run at 100% load across all cores and thus represents a maximum-usage scenario. After a few minutes, you’ll see your CPU hitting its peak temperature. The goal is to see how long it takes the CPU to become unstable while running at maximum load.

    Burning a CPU with a lighter is also a bad way to stress test a CPU.Stress testing your CPU will result in excess heat, but this isn’t the best way to do it.

    Preparing your PC for a proper stress test

    To make sure your stress test runs properly, you should prepare your PC:

    1. Close all non-essential applications: Background or foreground processes can conflict with the test. Closing programs and background processes is a great way to speed up your PC.

    2. Download and install AVG TuneUp, which identifies any programs that are hogging your RAM and CPU, slowing you down as a result. The newly revamped Sleep Mode technology puts those programs to sleep and grounds all background activity to a halt. That way, you’re free to run your stress test without wasting the resources you need.

    3. Open AVG TuneUp, go to Speed Up, and click on Background & startup programs. Sleep Mode will detect unnecessary programs and temporarily deactivate them to ensure your test delivers the most accurate results possible.

      Sleep Mode in AVG TuneUp

    4. Monitor: Keep an eye on temperatures. See our guide on why you should check and monitor your CPU. Don’t let it exceed 90°C for prolonged periods.

    What are the best tools to stress test your CPU?

    There are a number of programs you can use to stress test the processor. All of them work relatively similarly to one another, with minor differences. Let’s start with the top ones:


    As mentioned above, Prime95 is probably the most popular CPU stress testing tool out there, and it has been around for a while (we’re at version 28 now!). It employs the Mersenne prime technique, thereby making nonstop use of the processor’s FPU (floating point unit) and integer capabilities while also testing its various caches (L1, L2, L3).

    How to run Prime95

    1. Download Prime95. If you’re confused about which version to pick, choose the Windows 64-bit option, which is the basis for all newly built and bought PCs. Only PCs made in the 2000s, or extremely low-end machines from the early 2010s, run on 32-bit software.

      Downloading Prime95

    2. Launch the tool and select Just stress testing. Make sure to select the Blend option, which stress tests all cores and caches.

      Launching the Prime95 tool and selecting the Blend option to stress test your CPU.

    3. At this point, the test will begin. You’ll notice that your processor and all its cores will immediately reach 100% capacity, and that your computer’s fans will kick into action.

      Prime95 keeping all CPU cores busy

    4. Just like with other stress testing tools, it’s a good idea to let this one run for about an hour (or if you really want to know the maximum limits: a day!).


    With 25 years in the industry, AIDA is a massive suite of tools to display and diagnose your entire machine. It’s available as a premium product, but you can also download a free trial. AIDA64 features a wealth of information from every corner of your system — from dozens of temperature and voltage sensors to scheduled active tasks. 

    AIDA64’s system stability test simulates a more realistic workload. Here’s how to launch it:

    1. Download the AIDA64 trial. Extract the files and double-click on the AIDA64.exe file.

      Launching AIDA64

    2. If you want — and we recommend that you do — you can go through all the individual categories and explore the inner workings of your PC. For example, after selecting Memory from the Motherboard dropdown menu, you can see more details related to your machine’s memory.

      Run AIDA Extreme specifications

    3. In the Benchmark category, you can test your system and compare it to other PCs.

    4. But we’re not here to compare your PC to others out in the wild. We’re here to torture your processor. To launch this test, click on Tools and select System Stability Test. Ready? Click Start!

    5. Running AIDA stress test


      Note that during this test, you can easily switch back to the main AIDA64 window and go to Computer and Sensor. Here, you can watch over the CPU temperature and see how fast your fans are rotating.

      Checking temperatures with AIDA64

      As long as the temperature stays below 90°C you should be fine. Let it run for a few hours and see if your PC remains stable.


    Another favorite tool of mine is HeavyLoad. Keep the adage nomen est omen (“the name is a sign”) in mind with this one, as it doesn’t just stress test the CPU, but it also lets you monitor your GPU temp as your computer is put through its paces.

    Running HeavyLoad to test your CPU or GPU.

    Just launch the app, select CPU Usage, and hit the Play button at the top! That’s it.

    Intel BurnTest

    The Intel Burn Test isn’t an official Intel tool, but it’s one of the easiest stress tests out there to use.

    Intel Burn Test

    Open the app, click on Stress Level, and select Maximum. Hit the Start button. Let it run for a while and see if your PC can handle the stress.

    What if my PC fails the stress test?

    Then you’ve got a problem that’s either easily solvable, or it’s time for an investment:

    • Lack of cooling: Your CPU fan might not be adequate to cool down the processor. Look into upgrading the fan or even using watercooling if you’re not doing that already.

    • Dust bunnies: Your fans might be clogged with dust. Get an air duster or a vacuum and consider physically cleaning up your machine.

    • Aging hardware: Your PC might not be up to spec anymore, and its components could be showing signs of age. In my experience, this happens especially to PCs that have been overclocked and used for intensive tasks, such as gaming or video rendering, for at least five years. If you’re that enthusiastic, it might be worth considering an upgrade or even building your own PC for gaming, video editing, or whatever else you may need.

    • Outdated drivers or BIOS versions: Increased stress might also cause crashes on outdated drivers and BIOS releases. Check for new drivers or run a free scan with AVG Driver Updater. Then update the BIOS to the latest release.

    Stress testing: check! What’s next?

    Have you finished with your stress test? Now it’s time to make sure that not only your hardware is running smoothly, but your Windows operating system and software is, too. This is where AVG TuneUp comes in — it’ll keep your computer running like new with a full suite of specially designed performance-boosting tools. Try AVG TuneUp today for free and enjoy more power than you ever imagined!

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