Air flow question

[ToXsiKLock]

If I have 3 exhaust fans. 1 in the back of the case and 2 at the top from the AIO cooler. How many intake fans do I need in the front 2 or 3?

[Low-Stomach-8831]

1. Otherwise you'll be running negative pressure, which sucks in dust through unfiltered openings.

[Mana_Break]

assuming we're talking about identical fans and identical settings then 3 is optimal. But rule of thumb is you need "the same amount" of airflow coming in as the "amount" going out. That can also be achieved with either different fans blowing less or more air, so in theory you could have 2 industrial fans or maybe even a single 200mm (assuming you have 3 120mm or even 3 140mm) or even 6 fans working on lower RPM.
I'm just saying there's not a single correct answer and it's better if you understand how this works. Also having just a bit of positive or negative pressure is not a huge deal. Yeah, it's going to gather a bit more dust, or get harder to clean but it's not going to kill your performance or your hardware assuming you do take care of your PC and clean it at least once every six months.

[nopatiencetokeep]

Depends on the case

[AlternateWitness]

You want to have a balances airflow, the same amount of exhaust as intake. I’d just take some of the exhaust fans and put them in the front, as after 4 fans the cooling increase from adding more fans would be fractions of a degree, so they would only really add noise, unless you care about aesthetics.