120mm fans vs 140mm fans: Which fan size is better?

Almost all PC cases nowadays are designed to fit either 120mm or 140mm fans, and often they are capable of accommodating either size. This is a convention that the DIY PC industry has settled into after years of fans ranging from miniscule 80mm things to mighty 180mm lads.

So now that we’re down to two sizes: 120mm and 140mm. But which is better?

Per fan, you won’t be surprised to learn that a larger fan will produce more airflow. As an example, our iCUE LINK RX140 140mmproduces 95.7 CFM (Cubic feet per minute) of airflow when maxed out. This handily beats the iCUE LINK RX120 120mm, which maxes out at 74.2 CFM. Both of these fans have the same design and internals, by the way, so the only factor at play here is the difference in size.

However, the FANatics cry, there is more to a good PC fan than how much air it can blow, we also need to blow that air hard enough. Otherwise, it won’t get through fan filters, AIO radiators, or the fins of the heatsink of an air cooler

This is true, and how hard a fan blows is known as Static Pressure, often measured in mm-H20. Interestingly, when we again use the RX140 and RX120 fans, we see an inverse correlation between size and static pressure.

This time, the 120mm fan produces 4.38mm-H20 of static pressure, outperforming the larger fan, which produces 3.79mm-H20. This is interesting and counter intuitive. Perhaps a mixture of fan sizes is worth considering?

Before we talk about why mixing fan sizes could be a good idea, we should note that it isn't always simple. Very few cases are designed for the user to mount 2 fans of different sizes adjacent to each other. So you can use a mixture of fan sizes, but not in the same locations. For example you would realistically have to go all 140mm fans on the front, then all 120mm fans up top. The 4000D examples below illustrate this issue well.

Given that 120mm fans are generally better at static pressure and 140mm fans produce more airflow, it’s a great idea to use a mixture of both. Matching 120mm fans with radiators and heatsinks, and putting 140mm fans where airflow is unrestricted.

On the subject of radiators, it’s important to note that you must match the radiator size to the fan size. 120mm fans are not compatible with a 280mm radiator for example. The holes won’t line up. The same is true if you were to try mounting 140mm fans to a 360mm radiator. A quick compatibility matrix seems like a good idea right now.

Of course, now that gaming PCs are an exercise in aesthetics in addition to performance, a mixture of 140mm and 120mm fans might be a turn off for some, but that’s a question only you, the prospective fan purchaser, can answer.