[Custom PC] Differences in PC Case Fan Sizes

There are various specifications for case fans, such as size, airflow, and rotation speed. To improve cooling performance and quietness, it is important to choose the right case fan.

Among these, the size of the case fan is especially important. If the wrong size is chosen, it may not fit the PC case, or cooling performance and quietness may decrease. It is important to understand the differences by size.

Case fans generally have fixed sizes, and each has its own features and uses.

In most custom-built PCs, 120mm and 140mm are mainly used, but the differences between other sizes will also be explained in detail.

This article explains the basics of PC case fan sizes, airflow, direction, and functions, as well as how to choose from the perspective of performance and compatibility.

≫ Related article: How to Choose PC Case Fans for Custom PCs [Performance / Function / Compatibility]

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About Case Fan Sizes

First, the basic points about case fans will be explained.

Basically, 120mm/140mm Are Enough

Case fans come in various sizes from 40mm to 200mm, but for general custom-built PCs, 120mm and 140mm are most common.

Case fans are installed in PC cases, but the size of the case fan must be compatible with the case.

The sizes that are compatible with most cases are 120mm or 140mm, so these two sizes are usually chosen.

Some cases support larger sizes like 180mm or 200mm, but choosing a case for these sizes greatly limits the options. Therefore, choosing from 120mm or 140mm is more practical.

120mm and 140mm fans offer a good balance between cooling performance and quietness, so most people choose these sizes.

The difference between these two sizes is that the 140mm fan is larger than the 120mm fan, so it can move more air at the same rotation speed and tends to be quieter.

Share by Case Fan Size

The most common and popular PC case fan size is 120mm.

It was expected that 140mm would also be popular from the quietness perspective, but the result is surprisingly low.

The number of 140mm case fan products is about half to one-third that of 120mm, but the selection rate is even lower, so it seems they are simply less popular.

≫ Related article: Popular PC Case Fan Rankings and Selection Rates by Specification [Statistics]

*This data is based on parts selected by users in the Custom PC Tool, which allows for “estimation“, “compatibility check“, and “power calculation” just by choosing parts.

Larger Sizes for Quietness

If quietness is important, it is crucial to choose a larger case fan.

Fan noise is caused by high rotation speed, so quietness depends on how low the rotation speed can be kept.

The larger the case fan, the less rotation speed is needed to move the same amount of air.

This keeps the fan noise lower and improves quietness.

Larger fans can move more air efficiently, so cooling performance also improves.

On the other hand, smaller fans need to spin faster to provide the same airflow, so they tend to be noisier.

On Pasolog, manufacturer PCs are borrowed and their performance and quietness are measured and reviewed.

After listening to the sounds of various fan sizes, it is clear that larger case fans are quieter.

For example, a stock CPU cooler has a small 92mm fan, but just a little load increases the rotation speed and makes it noisy.

Although CPU coolers and case fans have different purposes and cannot be compared directly, the noise difference by fan size is clear.

There is also an explanation on how to choose parts for those who want to build a quiet custom PC.

≫ Related article: How to Choose PC Parts for a Quiet Custom PC [Causes and Solutions]

Larger Sizes for Cooling Performance

Larger case fans are also advantageous for cooling performance.

As explained, the larger the case fan, the less rotation speed is needed to provide the same airflow. Conversely, increasing the rotation speed increases airflow.

Although the maximum rotation speed differs by product, basically, larger sizes tend to have higher cooling performance.

List of Case Fan Sizes

Case fans come in various sizes from 40mm to 200mm.

Focusing on the common 120mm and 140mm sizes, other sizes and their uses will also be explained.

[Standard Sizes] 120mm/140mm

120mm and 140mm are the most commonly used sizes for PC case fans.

Most PC cases support these two sizes, and many cases are designed to allow installation of either 120mm or 140mm fans.

These sizes offer a good balance between the size of the case (the computer itself) and cooling performance.

Looking at the graph again, about 80% of people choose 120mm, making it overwhelmingly popular.

Next is 140mm, at about 15%.

So, while 120mm and 140mm are both standard sizes, 120mm is the most common.

However, as mentioned earlier, if quietness or cooling performance is important, 140mm is recommended.

The 20mm difference does not make a dramatic change, but most PC cases support 140mm as well.

Therefore, 140mm can be chosen to improve quietness and cooling performance without greatly limiting case options.

[Large Sizes] 180mm/200mm

Large fans of 180mm and 200mm move more air and are quieter than standard 120mm or 140mm fans.

Even at low speeds, they can provide enough airflow, so they can cool efficiently while keeping noise low.

Large sizes are about 1.5 times bigger than standard sizes, so they are quite large.

To install these sizes, the case itself must support them, but due to their size, compatible cases are limited.

For example, mid tower cases are about 200mm wide, so to install a 200mm fan, a larger mid tower or a full tower case is needed.

In fact, the number of PC cases that support large sizes is less than 10% of those for standard fans.

As such, compatibility is very different from standard fan sizes.

Choosing a case design is one of the joys of building a custom PC, but if a large fan is desired, options are limited.

Therefore, these sizes are for those who want to prioritize quietness or cooling performance even if it means fewer case choices.

[Small Sizes] 40mm/60mm/80mm/92mm

Small case fans of 40mm, 60mm, 80mm, and 92mm are mainly for small PC cases or servers.

These sizes are suitable for environments where space is limited but cooling is needed.

Stock CPU coolers sometimes use 92mm fans, but these sizes are rarely used in general custom-built PCs.

Also, small fans tend to spin faster than large fans, so they are noisier.

For servers, the PC is usually placed in a server room, separate from the user, so noise is not a problem even if the fan spins fast.

However, for consumer use, the PC is often placed near the user, so the noise is heard directly.

In other words, small fans are suitable for servers, not for general consumer custom PCs.

Summary: 140mm Is the Most Versatile and Recommended!

This article explained commonly used PC case fan sizes, share by size, and what changes with different sizes.

Here are the key points again.

Basically, there is no problem choosing from 120mm or 140mm, which are compatible with most PC cases.

Of course, it is important to check the specifications to make sure the case supports the size, but most cases do.

If quietness and cooling performance should be improved without limiting case options, 140mm case fans are recommended.

If it is acceptable to have fewer case options and these features are prioritized, large sizes like 180mm or 200mm are also recommended.

However, depending on the parts configuration, as long as there are enough fans (at least 2 or 3) and airflow is secured, 120mm fans will not be uncomfortably noisy, so 120mm is also a good choice.

Based on these points, consider the design and budget of the case fan as well.

This article also explains the basics of PC case fan sizes, airflow, direction, and functions, as well as how to choose from the perspective of performance and compatibility.

≫ Related article: How to Choose PC Case Fans for Custom PCs [Performance / Function / Compatibility]

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PC Parts Estimation & Compatibility Check Tool

Automatically checks each component you need when selecting parts for a custom-built PC—perfect for beginners.