Computer Fan Dimensions – Choosing The Best Fan For Your PC


Computer Fan Dimensions Choosing The Best Fan For Your PC

So maybe you have a custom rig you plan to build, or you went to turn your computer on and one of your fans didn’t spin up. Either way, you’re now looking for fans for your case. There’s a lot out there and you have a lot of choices to make. But how do you start? What size do you even buy? Do you want a loud fan that pushes a lot of air or a quiet fan that won’t disturb you? These are excellent questions that we will answer in this article.

Typically, fans used to be and an under looked and under appreciated aspect of a computer case. They did their job and kept the insides of the system cool, but otherwise, not much thought was given to them otherwise. In more recent years, they’ve started to become more prominent in computers as part of a whole or completing a theme rather than just an after thought.


The Ins And Outs Of Fans

PC Fans have several design aspects to them and it’s great to have an understanding of these specs when you’re looking for new fans or replacement ones. Some of these specs can come down to personal preference or their need be necessitated by the computer, but regardless it’s still important to know what you’re looking for!

Below I’ll give you a solid rundown of certain key specs of a fan so you have a better idea of what you’re looking at.


dBA – Otherwise known as decibel level. Usually this will be listed somewhere on the box the fan comes in, or if you’re ordering online, somewhere in the details of the product. This is just going to let you know how quiet or loud a fan is in general. A fair word of warning, however, manufacturers are sometimes very reserved with their dBA rating. Look at it more like an estimation than a fact.

Amps – A simple way of knowing how much power the fan is going to draw while it’s running. In order to find out the maximum wattage the fan will draw, you can simply multiply the amps by the voltage. A quick example would be 14 amps x 12 volts = 1.68 watts.

RPM – Revolutions Per Minute. This will give you a clear indication of how many times the fan will do complete rotations in a minute. The higher the RPM stated, the faster the fan will rotate. Keep in mind, a faster fan generally equates to a louder fan as well!

Static Pressure – This a more complicated spec at first glance that is measured in units of mmH20. If you’re newer to system building or understanding fan specs in general this might seem weird at first. This is an important spec, however, if you plan to be placing the fan next to components that would typically obstruct airflow. The higher the static pressure, the more force the fan can exert.

CFM – Cubic Feet per Minute. This is a measurement of how quickly a fan can move volumes of air through its blades. The higher this measurement, the better the fan is at keeping things cool.


Once you have a general knowledge of these specs, it can make picking out fans a breeze. Of course, there are other things you might want to consider when you’re looking for a new fan, like LED Computer Fanaesthetics. Fans offer much more in the way of choices for looking more interesting these days than they used to. There are two main aesthetic choices you might encounter.

RGB – Otherwise known as LED fans. These fans typically have either single color or multiple colored lights in them, which can greatly increase the visual appeal of your case.

Colored Rings – These are single color plastic rings that are typically interchangeable to help match the colors of components inside your computer. These usually do not light up, but if you don’t want to worry about a light dying out on your fan, these colored rings are a solid choice.


Fan Sizes And How To Find Them

Since you now have a better idea of what kind of fan you’re looking for, you should probably find out what size to get. But how do you find that out? There’s two easy ways to tell what fan size you need for your case. The physical box the case comes in will have fan sizes and dimensions printed somewhere on it (it should also have it in the details of the product if you’re ordering it online). If that’s not an option for you, then bust out your measuring tape!

If you have a fan on you, simply measure the fan edge to edge. Make sure to measure horizontally across and not diagonally. Also, keep in mind that fan measurements are taken in millimeters, not inches. You might be able to find some that are converted, but it’s much easier to stick with the industry standard in this case!

But what if you don’t have a fan available to measure? Not to worry! There’s still a way to figure this out, but it will require you to measure the screw holes on the case where you would be mounting a fan. Just like with the actual fan, measure horizontally, but this time you will want to measure from the center of one screw hole to the other. You’ll also probably find that the measurements taken here are not the same as what might get with an actual fan. I’ll break down the most common screw hole and fan measurements below so you can match them up!


32mm between each of the screw holes: 40mm fan size
40mm between each of the screw holes: 50mm fan size
50mm between each of the screw holes: 60mm fan size
60mm between each of the screw holes: 70mm fan size
72mm between each of the screw holes: 80mm fan size
83mm between each of the screw holes: 92mm fan size
105mm between each of the screw holes: 120mm fan size
124mm between each of the screw holes: 140mm fan size


There are fan sizes that go further above 140mm, however these are much more rare. There are sizes all the way up to 250mm and even more, but these more unique fan sizes are generally offered as expansion options for larger cases. If you’re buying one of these bigger fans, you likely already know what you’re searching for.


Wires And Pins And What They Mean

Another key aspect of a PC fan is the wires that it comes with. It might be a little confusing to look at them and not be able to tell one from the other, but it’s actually quite easy to break them down into three main categories.

4 Pin Connector – Like its name suggests, this is a connector with four pins and is likely the largest connector that comes with the fans. This plugs straight into the power supply which will run the fan at its maximum speed. You won’t have anyway to control this speed, but generally this will get the job done regardless.

3 Pin Connector – Again, this is just a three pin connector. It’s smaller than the four pin and connects directly to your motherboard. Powering your fan this way allows for your computer to monitor the RPM and health of the fan itself and can even warn you when things are going wrong. This connector can also be plugged into the power supply itself with an adapter, but not all fan kits come with one.

4 Pin PWM Connector – This is a smaller connector like the three pin, but once more like the name implies, it has four connectors. This fourth pin is used by newer motherboards and will allow the motherboard to directly control fan speed without the need for any adapters or voltage adjustment in the BIOS.

If you have the option to use a 4 pin PWM connector, you definitely should. These give you much more sophisticated control over your fans. However, motherboards can sometimes have pretty limited connection ports for these fans, so if you’re using a lot of fans, you may not have the ability to plug them all into the motherboard. Make sure you plan ahead of time in this case to know which ones you want to hook up to your motherboard and which ones you plan to plug directly into your power supply!


Which Way Do You Face The Fan

I feel this is a question that a lot of people have but are afraid to ask. It’s nothing to be ashamed of and It’s really not too complicated, but a lot of the time it may not be too obvious at simply glancing at the fan itself. There’s two easy tricks though to quickly figuring out which way the fan is going to move air.

Firstly, check the plastic sides of the fan itself. You will likely find somewhere on the fan a pair of arrows. One pointing up or down, and the other arrow pointing left or right. The arrow going up or down is telling you which way the blades of the fan are going to be spinning. The arrow going left or right is letting you know which way the air is going to be moving through the blades. If you want more air going in, mount the fan with the arrow pointing into your case. If you want air being pulled out, mount the fan with the arrow pointing out.

But wait, your fan doesn’t have arrows on it? No problem! An even easier way to tell which way to face your fan (and one I personally use) is to simply look at the two sides of the fan. One side will show you the blades, and the other will show you brackets that hold the fan motor in place. The fan will be blowing air out through the side with the brackets, so if you want it to be an exhaust fan, face the brackets out. If you want it pulling air in, flip it around. Simple!


Being A Fan Of Fans (Conclusion)

Because fans are usually such an overlooked aspect of a computer build, many people tend to never learn the interesting details of fans and fan dimensions. There’s lots of little things to learn about them that can make choosing a good fan for your PC quick and easy.

With all the options available to you, and with this new knowledge you’ve acquired, you should have no problem going out and finding new fans that will be a perfect fit for your case. Whether you’re looking to beef up the cooling in your case, bring some color to it, or simply replace a broken one, there’s definitely a fan out there for you!

If you have any questions or comments, please feel free to leave them below and I will get back to you!


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