Reverse blade fans exist for one reason: looks. In a glass case, a normal intake fan shows you its back, with the struts and the sticker. A reverse fan shows the clean blade side instead, while still pulling air in.
That’s handy, but it also breaks the usual trick for telling which way a fan blows. Here’s where they belong and how to install them right.
Where reverse fans go
Use a reverse fan anywhere you’d otherwise see the back of an intake fan. Use normal fans everywhere else.
| Fan spot | Fan type | Set it to |
|---|---|---|
| Bottom, under a glass side | Reverse | Intake |
| Side, on the motherboard tray side | Reverse | Intake |
| Top | Normal | Exhaust |
| Rear | Normal | Exhaust |
Corsair says reverse fans belong anywhere you would see a standard intake fan from its back, which is often the bottom and the motherboard side. Lian Li makes the same point for its SL-INF Reverse, which is made for the bottom of the case or on top of a radiator.
Which way does a reverse fan blow?
On a normal fan, air leaves through the side with the sticker and the struts. Noctua puts it simply: with the sticker facing you, the air blows toward you.
A reverse fan flips that. Phanteks describes its regular D30 as moving air front to rear, and the reverse version rear to front. So on a reverse fan, the air leaves through the clean blade side.
The safe way to check any fan is the small arrows on its frame. One shows the spin, the other shows the airflow. Our fan direction checker walks you through it for normal and reverse fans.
Do reverse fans move less air?
Usually a little, but not always. Here are four pairs, straight from the makers’ spec sheets:
| Fan (120 mm) | Airflow, normal vs reverse | Pressure, normal vs reverse |
|---|---|---|
| Phanteks D30 | 64.3 vs 61.5 CFM | 3.01 vs 2.72 mm H₂O |
| Lian Li UNI FAN TL LCD | 62 vs 54.3 CFM | 2.9 vs 2.83 mm H₂O |
| Lian Li UNI FAN TL | 90.1 vs 83.4 CFM | 3.97 vs 2.66 mm H₂O |
| Lian Li UNI FAN SL-INF | 61.3 vs 63.6 CFM | 2.66 vs 2.02 mm H₂O |
Three of the four reverse fans give up some airflow, and one gains a little. They can also run a bit louder: the D30 Reverse is rated at 31.8 dBA against 30.2 for the normal one.
The gap is small on an open bottom mount. Where the fan has to push through a radiator or a dense filter, the lower pressure matters more.
Do you even need them?
Only if you’ll see the fan. A normal fan pulls air into the case just as well. It just shows you its back while doing it.
If a fan sits where nobody looks, like behind a solid panel, a normal fan usually gives a little more air for the same money. To see how much louder a set of reverse fans will be, try our fan noise calculator, which has the Phanteks and Lian Li pairs built in.
Related guides
- Bottom intake fans, and when fans under the graphics card are worth it.
- Dual chamber case setups, where reverse fans are most common.
- Hyte Y70 setup and Phanteks NV7 setup, two glass cases with bottom and side intakes.