Can you use a CPU fan as a case fan? (Complete Guide)


A few weeks ago, I realized I had a leftover CPU fan after upgrading my gaming PC’s CPU. As the type of gamer always looking to push the boundaries of amateur overclocking, I always like to stuff as many cooling fans into computer case as possible. So a question popped into my head: could I use my leftover CPU fan as an extra case fan? Determined to find an answer, I plugged the CPU fan into my motherboard. This is what I found:

Yes, you can use a CPU fan as a case fan. CPU Fans do tend to run at a higher RPM than case fans. CPU Fans run at 3000 RPM or higher, and case fans tend to hover around the 1200 RPM range. This means the CPU fan will be slightly louder. 

Ok, now you know a CPU fan can be used as a case fan. However, there are so many other questions that need answering.

In the article, I’ll be covering:

  • Whether or not you can use a CPU fan as a case fan.
  • Can a case fan be used as a CPU fan?
  • The difference between a CPU and a case fan.
  • Are there any universal fans?
  • And, whether or not you need case fans if you have a CPU fan.

Let’s start the article by answering whether you can use a CPU fan as a case fan in more depth.

Can you use a CPU fan as a case fan? 

In this section, I’ll explore whether or not you can use a CPU fan as a case fan. 

This is a question that many people have, and the answer is yes, you can. In fact, using a CPU fan as a case fan is a great way to keep your computer cool.

The first step is ensuring your CPU fan is the right size for your case fan slot. Most CPU fans are 12cm or 120mm, so you’ll want to ensure that your case fan slot is that size or larger. If not, you should consider replacing your CPU fan with another case fan that is the right size.

Also, remember that CPU fans operate at a higher RPM than case fans. CPU fans spin at approximately 3000 RPM, and case fans spin at around 1200RPM.

The CPU fan will push more than double the amount of air into your case compared to a case fan of the same size. However, the CPU fan will be louder as it’s turning quicker and moving more air.

The CPU Fan can be plugged into the regular motherboard fan headers. They are easy to spot as they have two pins next to a small flat piece of plastic. And you should see the word FAN clearly printed on the motherboard.

Some CPU fans come with larger connectors than what the motherboard’s fan headers can take. This is often because the CPU fans have sensors that help the motherboard BIOS to detect the fan’s RPM.

If the connector is wider than the motherboard’s regular fan headers, that’s ok. The fan connector should still fit the fan header on the motherboard and work when you start your PC.

In this section, you learned that it is possible to use a CPU fan as a case fan.

In the next section, we’ll look at whether or not it’s possible to do the opposite: Can a case fan be used as a CPU fan.

Can a Case Fan be Used as a CPU Fan?

Yes, you can use a Case fan as a CPU fan.

However, a case fan, in many scenarios, is not a good option to use as a CPU fan. This is because a fan built for CPU cooling usually operates at a much higher RPM than a case fan.

As mentioned above, the average CPU fan operates at 3000 RPM. The average case fan operates at 1200 RPM.

This means that a case fan of the same size moves 60% less air than a similar-sized CPU fan.

A case fan is massively less efficient at pushing air across the CPU’s cooling block when compared to a CPU fan.

This can cause a CPU rapidly overheat.

Case fans use a lower RPM because it’s expected that in a gaming PC, you’ll use 3 fans to push air into the case. This means these 3 fans can work together to move a large volume of air at lower and quieter RPMs. Plus, if you create a positive pressure atmosphere in the case, this will help push hot air out of the top of the case and further increase the volume of fresh cool air flowing in the case.

On the other hand, the CPU fan is directly responsible for moving large volumes of air over the CPU’s cooling block to wick away heat. Without a high enough air volume, the heat won’t be removed quickly.

Therefor, I recommend using a purpose-built CPU Fan with your CPU cooler.

In this section, you’ve learned that you can use a case fan as a CPU cooler. However, you shouldn’t, as the case fan will not shift enough air volume to cool the CPU efficiently.

In the next section, we’ll examine the difference between a CPU fan and a case fan.

Is there any difference between CPU Fans & Case Fans?

In the last section, you learned that case fans don’t make good CPU fans because of the low volume of air they move compared to CPU fans.

In this section, I’ll look at the main differences between CPU fans and case fans.

There are several differences between CPU fans and case fans.

I’ve listed them below.

The first thing people will notice between a CPU fan and a case fan is the RPM or revolutions per minute. Case fans run at much lower RPM than CPU fans. CPU fans usually run at 3000 RPM, while case fans run at 1200RPM, which is 60% lower. This directly means that less air is being pushing by the fan into your CPU or PC case.

They are also designed differently. The airflow of a CPU fan is designed to push large volumes of cool air directly into the CPUs heat sink block, and do so with no regard for noise levels. It’s believed that because the CPU fan is deep within the PC case, any sound will be muffled.

Case fans are designed to push hot air out of the PC and pull cool air into the PC. However, they operate at lower RPM to do their work quietly.

The blades of these two fans are also designed differently. The blades of a CPU fan are designed to move a high volume of air without worrying about noise generation. The blades of a case fan are designed to move the maximum amount of air for the lowest RPM to decrease the amount of sound generated by the case fan.

So the two main differenced between the two fans is the volume of air they shift and the noise levels they produce.

Another difference is the price. The average price of a CPU fan is $30-$50, while the average price of a case fan is $5-$20. The case fan is thus much more affordable as it is cheaper.

However, remember that a CPU fan often comes with the CPU’s cooling block and mounting bracket, both of which push the price up of a CPU fan.

Additionally, there is usually a difference in size between CPU fans and case fans.

Usually, CPU fans are 12 cm across or 120 mm. They can be even smaller than this in compact PC cases. The CPU fans are relatively small, allowing them to fit in the tight spaces around a CPU. Their small size enables them to fit on top or at the side of a CPU cooling block.

Conversely, case fans can come in many sizes. For example, I have two Gaming PCs with significantly different fan sizes. One of my Gaming PCs, which uses a Thermaltake cube case, has a large 22 cm fan. That’s nearly double the size of a CPU fan. Because of it’s large size, It acts as the only fan pulling air into the system. My other case, which is an NXT case, has 2, 14cm fans.

So case fan sizes tend to vary significantly compared to CPU fans.

In this section, we learned that CPU fans and case fans are often very different.

However, in the next section, you’ll learn that there is such a thing as a universal fan. These can be used as a CPU fan or a case fan.

Let’s take a look.

Is there a one-size-fits-all Universal Fan for both CPU & Case?

In the last section, you learned about the differences between case fans and CPU fans.

In this section, we’ll explore universal fans that can be used as both CPU and case fans.

Yes, there are a number of one-size-fits-all fans.

One of these fans is called the Noctua NF-A14.

The Noctua NF-A14 is a 14cm fan designed to be used as a CPU fan or a case fan. However, given the 14cm size, the Noctua NF-A14 can only be used with the largest CPU coolers.

It spins at a maximum speed of 1500 RPM, which is well within the optimal RPM range for case fans. You’d think this would be a little slow for a CPU fan. However, Noctua has engineered the fan’s blades to move far higher volumes of air than the fan’s size or speed would suggest possible.

It can move 140,2 m³ of air per hour while only generating up to 24.6 dBA noise.

The fan comes with a three-year warranty, which shows how confident the manufacturer is in the quality of the fan. 

However, Noctua isn’t the only company making universal fans.

For example, Corsair and Coolermaster now make Universal PC fans that can be used as either case fans or CPU fans.

Now you know that universal CPU/case fans do exist. However, I recommend buying a specialist CPU fan for cooling your CPU. I wouldn’t use a case fan or universal fan for an expensive CPU. I want something purpose-built for the job.

In the next section, I’ll examine whether you need any case fans if you already have a CPU cooler fan.

Do You Need Case Fan If You Have a CPU Cooler?

In the last section, I discovered that a universal PC fan can be used as either a case or CPU fan.

In this section, I explore whether or not you need case fans if you already have a CPU fan.

If you are building a gaming PC, you need extra case fans to provide fresh cool air to the CPU fan, the GPU fan, and the other components.

This fresh cool air is pulled into the case by case fans.

Additionally, you need extra case fans positioned at the top of the case to help blow out the hot, dirty air produced by all the components.

A GPU and CPU will run much hotter if you have no case fans pulling in that cool air.

As a general rule of thumb, you should have 3 case fans pushing cool air into the case at the bottom front of the case.

Then you should have 2 fans extracting hot air from the top of the case.

You should have 3 fans pushing air in and 2 fans pushing air out because you should have a positive air pressure inside your PC case. This helps in 2 ways:

  1. The denser the air is, the better it can wick away heat from your components.
  2. The positive pressure constantly pushes hot air out of the system’s top.

So yes, generally speaking, you always want to be using case fans.

Ok, so in this section, you learned that you should always use case fans with a gaming PC.

In the final section, I’ll summarise the entire article.

Summary

Wow, that’s a lot of talk about CPU and case fans. I can’t remember half the stuff I’ve talked about. Good effort if you can. However, if you can’t, don’t worry. I’ve included a handy bullet-point summary below.

  • Yes, you can use a CPU fan as a case fan
  • The CPU fan will be loud because it spins at a high RPM.
  • You can use a case fan as a CPU fan. However, you shouldn’t because case fans do not shift enough volume of air to cool the CPU efficiently.
  • Some universal fans can be used as CPU and case fans.
  • Yes, you need case fans even if you already have a CPU fan.
  • Always use 3 fans that push cool air into the case and 2 fans that pull hot air out.

As always, I hope this article has helped you.  

If you’ve found this article helpful, please share it!

Thanks for reading! Please comment below if you have any questions, ideas, or feedback.

Nick Sinclair

Having played games since the golden age of the Commodore 64, Nick finally took the plunge and studied Creative Game Design in university. After 3 years of "Study", Nick co-founded a games company where he soon discovered his true calling: writing about games. 11 years later Nick writes about a tower of topics, but gaming is always stacked neatly at the top.

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