How to Measure PC Fan Size [ 2021 Update ]

On most modern fans, you will find 2 arrow indications: The vertical arrow indicates the direction in which the blades rotate. You will know how to measure PC fan size.

How to Measure PC Fan Size

The horizontal arrow indicates the direction of the airflow.

Don’t worry if these arrows are missing on the fan. A simple way to test the direction of the airflow is to place a piece of tissue in front of the fan and see which direction it goes: whether it gets sucked in by the fan or blows away.

Airflow

The “power” of a fan is measured in CFM (cubic feet per minute). The higher this number, the more air the fan can move. Usually:

  • Fans with more than 70CFM are considered high airflow fans.
  • The “normals” usually range between 20 CFM and 70 CFM.
  • Anything less than 20CFM is weak.

Noise

Measured in dBA. Yes, noise and sound are generally measured in decibels (dB). But in simple terms, dB doesn’t make a lot of sense to fans.

Therefore, they are weighted relative to air and therefore in A-weighted decibels (dBA).

  • 25 dBA refers to the volume of a person whispering in a library.
  • Average computer fans generally generate between 30 dBA and around 40 dBA of noise (audible hum).
  • So yes, any fan that is rated less than 30 dBA is considered quiet.

Fan speed

The speed at which the fan spins is measured in rounds per minute (RPM). I think this is a not-so-useful spec.

Generally, the faster a fan spins, the more airflow it generates. But at the same time, it also generates more noise, consumes more power, and wears out the fan faster. However, all of these are subjective. Some fans are designed to run at high speed, and some fans don’t need a lot of speed either to generate good airflows.

Power Rating

This is something you should be very careful about if you plan to do some DIY – the Molex power connectors on the power supply are usually 12V, and the USB runs on 5 ~ 12V.

  • Trying to run a 12V fan on USB 5V is insufficient … The fan will spin very slowly or not even work.
  • Vice versa, running a 5V to 12V fan will likely burn it out.

How about CPU and Graphics card fans?

  • The dimensions of the case fans are practically standard. But when it comes to the CPU and graphics card heatsink, it seems to be fair game.
  • Each manufacturer has its design vision, and there doesn’t seem to be a “fixed size” or “fixed design” anywhere. But hey, it’s good news that people come up with a lot of different cooling solutions

Pick the right size up

The design of each computer case is different and there is a predetermined number of slots where you can mount additional fans. The only way to find out is to open the computer case and measure the size of the fan slots. A little annoyance, but it prevents you from buying fans that don’t fit.

You got how to measure PC fan size in 2021.

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