PC Airflow Guide: How to Set Up and Position Your Fans

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Arranging your case fans properly helps your system run at peak performance. Here’s how to do it.

Set Up PC Case Fans
(Image credit: Tom's Hardware)

Computers rely on a steady stream of cool air to perform their best. There are many ways to arrange your case fans, and relying on the case or system manufacturer to choose that for you isn’t always the best choice. Opening up your PC case and rearranging components can be a daunting task. We’re here to help.

The good news is that fans are one of the simplest components inside your PC. They’re usually connected to clear mounting points and use only four screws to attach. Each fan uses a single connector for power, plus another if it has customizable RGB. There are a few things you need to know to get started organizing and arranging your fans. But once you do, arranging them for peak performance isn’t difficult or exceptionally time consuming.

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Christopher Coke
Christopher Coke
Contributing Writer

Chris is a regular contributor for Tom’s Hardware, covering mechanical keyboards, peripherals, and content creation gear for many years. He has been a tech enthusiast since the early 1990s and has been a regular contributor to a number of publications, including Tom’s Hardware, IGN, Popular Science, Reviewed, and PC Perspective.

34 Comments Comment from the forums
  • Soaptrail
    In my old case i used the front AND top as intake fans, it worked well since my front of my case had too much blocking the flow of air. As long as the rear exhausts the air it works.
    Reply
  • gan14
    I just have to ask. Where did you get these crazy ideas from when you wrote this article.

    "Pressure" does not build in computer cases full of wholes. Warmer air also doesn't have time to "travel upwards" in a case where it is ejected in a few milliseconds. If warm air traveled upwards at the speed you think it does, buzzards using updrafts would be ejected into the stratosphere. If you did some tests instead of making MS Paint images, you could have figured those things out by yourself.
    Reply
  • TR909
    For the AIO - putting your AIO in pull configuration gets the best cooling for the CPU, in the expense of some higher temps for the GPU - in Push configuration the radiator (being at the top) is fed with hot air coming from CPU, GPU, etc. so not ideal and not really convinced that manufacturers propose this as the 'best case'.
    Reply
  • Matt_ogu812
    "...............time you are taking off your side panel to do something inside your system, be sure the system is powered down and unplugged."

    So sad to have to tell people common sense things like this.
    Reply
  • lmcnabney
    Water cooling systems moving into the case has been a baffling move. When they first gained popularity the water lines would EXIT the case so that the radiator for the CPU's heat did its thing outside of the case. That way the entire case ventilation can be designed to cool the GPU/chipset/RAM without having to worry about the CPU. By having the radiator inside of the case it is either going to be dissipating CPU heat out of the case using pre-heated case air or be more effective cooling the CPU by bringing in external air, but then dumping all of that heat right into the case to make life hard on the GPU. The only good solution is to watercool both the CPU and GPU and blow the radiator(s) out of the case. That way the two big heat generators are having their heat ejected.
    Reply
  • wmeyer
    Odd notions in the article with respect to "ideal" configurations. As this is supposed to be a technical discussion, I will assume that all can deal with terms like "eddy currents."
    Q: Given a pipe, will it be better to blow air in, or suck it out? A: Assuming the pipe is a simple shape, it won't make much difference. What goes in must come out.
    Add some elbows, say three 90 degree turns, and the situation changes. It will be somewhat better to exhaust than to blow in. The reason is that pressurized air hitting the sharp turns will set up eddy currents and these will impede the flow. With an exhaust fan, the air seeks the easiest flow path, and the relative efficiency increases.

    Consider then a PC. Multiple intake ports and exhaust ports. Numerous internal obstructions. Exhausting the air will be more efficient. It will also be quieter. Besides the obvious ports, most cases will have leaky gaps through which air may also flow.

    A terrible example would be to blow air in through the front of the case where it immediately hits disk drives or other structural obstacles. Those will always create eddy currents.

    A simple way to test things is to use smoke. You can purchase smoke tubes, or simply use a lighted cigarette. Moving the smoke source to the vicinity of an intake port you can see how well the air flows. At what distance does the flow cease to deflect the smoke?

    Many years ago, Pamotor, a fan manufacturer, offered application notes on how to make cooling most efficient. These days, such references are more difficult to find.
    Reply
  • Greg7579
    gan14 said:
    I just have to ask. Where did you get these crazy ideas from when you wrote this article.

    "Pressure" does not build in computer cases full of wholes. Warmer air also doesn't have time to "travel upwards" in a case where it is ejected in a few milliseconds. If warm air traveled upwards at the speed you think it does, buzzards using updrafts would be ejected into the stratosphere. If you did some tests instead of making MS Paint images, you could have figured those things out by yourself.
    The author is correct in the way he described this in the very good article. There are nuances and every case is a bit different, but the best way to design airflow in a PC is the way he described it.
    I've had this discussion with fellow PC builders several times in the past and there are arguments about how best to design the flow, but in my opinion the author nailed it.
    I study high end builds constantly and am amazed at the way some serious enthusiasts place their fans.
    The bottom line is if you have a lot of fans in a good case and use an AIO, it is going to cool pretty well even if you screw up the air flow. I just can't imagine why a few of my fellow PC building enthusiasts push hot air into the case through the radiator. I just saw a high-end build that did that....

    I think the article is really good and teaches the basics very well. I think he should have mentioned the fan on the PSU because I see a lot of upside-down PSUs for various reasons. In fact, I just built one that way! LOL.
    Reply
  • Greg7579
    wmeyer said:
    Odd notions in the article with respect to "ideal" configurations. As this is supposed to be a technical discussion, I will assume that all can deal with terms like "eddy currents."
    Q: Given a pipe, will it be better to blow air in, or suck it out? A: Assuming the pipe is a simple shape, it won't make much difference. What goes in must come out.
    Add some elbows, say three 90 degree turns, and the situation changes. It will be somewhat better to exhaust than to blow in. The reason is that pressurized air hitting the sharp turns will set up eddy currents and these will impede the flow. With an exhaust fan, the air seeks the easiest flow path, and the relative efficiency increases.

    Consider then a PC. Multiple intake ports and exhaust ports. Numerous internal obstructions. Exhausting the air will be more efficient. It will also be quieter. Besides the obvious ports, most cases will have leaky gaps through which air may also flow.

    A terrible example would be to blow air in through the front of the case where it immediately hits disk drives or other structural obstacles. Those will always create eddy currents.

    A simple way to test things is to use smoke. You can purchase smoke tubes, or simply use a lighted cigarette. Moving the smoke source to the vicinity of an intake port you can see how well the air flows. At what distance does the flow cease to deflect the smoke?

    Many years ago, Pamotor, a fan manufacturer, offered application notes on how to make cooling most efficient. These days, such references are more difficult to find.

    Disagree on your "blow air through the front" comment. I would probably never exhaust out the front unless I had a radiatir there. I suck in with three big fans in the front and exhaust out the back and through the AIO on the top. I suck in from the front and bottom every time. But I build with expensive cases with good filters. I like pos pressure in the case to force air out through the tiny unfiltered spaces to keep it cleaner. All air coming in via fans is through a filter.
    Reply
  • Greg7579
    TR909 said:
    For the AIO - putting your AIO in pull configuration gets the best cooling for the CPU, in the expense of some higher temps for the GPU - in Push configuration the radiator (being at the top) is fed with hot air coming from CPU, GPU, etc. so not ideal and not really convinced that manufacturers propose this as the 'best case'.
    I have had this argument many times and I think you are wrong. I have never understood the argument. Never suck air into the case through a hot radiator. Never.
    The author is correct. (Maybe I misunderstood you.)
    Reply
  • newtechldtech
    Greg7579 said:
    I have had this argument many times and I think you are wrong. I have never understood the argument. Never suck air into the case through a hot radiator. Never.
    The author is correct. (Maybe I misunderstood you.)

    sadly the author and many of the people never use wind tunnels with AIO in which sucking the air into the case is the best but then wind tunnel them to the near top fans.

    Sadly all what people do here is standard Mounting without any ANY innovation.

    the best cooling is rad to the front taking in air and then wind tunnel to the nearest top fan front) and and optional rad at the top optional )
    Reply