Case Airflow Calculator
Check your case has enough airflow. Calculates total CFM, air changes per minute and positive or negative pressure, with fan placement tips.
Getting case airflow right
A case does not cool components; it supplies them with cool air and removes the hot air they produce. Every watt your hardware consumes becomes heat inside that box, so the volume of air moving through it has to keep pace with the heat going in.
Front in, back and top out
Heat rises, so the configuration that works almost everywhere is intake at the front, exhaust at the rear and top. Fighting that natural direction — exhausting at the front, for example — makes things worse for no benefit. Keep the path short and unobstructed.
Positive pressure keeps dust out
With slightly more intake than exhaust, air leaves through every gap in the case rather than being pulled in through them. Since your intakes have filters and the gaps do not, positive pressure means far less dust inside. The trade-off is marginally warmer temperatures than a pure high-flow setup, which is usually worth it.
More fans is not automatically better
Beyond about six, additional fans add noise faster than they add cooling, and fans working against each other can create dead spots. Two good intakes and one exhaust, running slowly, outperform six cheap fans at high speed — and are far quieter.
Static pressure versus airflow
Fans mounted against a restriction — a radiator, a dense dust filter — need static pressure. Fans in open positions need airflow. Using an airflow-optimised fan on a radiator wastes most of its capability, which is a common and invisible mistake.
The graphics card dumps heat inside
Modern open-cooler cards exhaust into the case rather than out of the back, so a 350 W card is a 350 W heater sitting in the middle of your build. That heat has to leave somehow, and it is the main reason a powerful card also raises CPU temperatures. Check its draw with the PSU Calculator.
Frequently asked questions
How many case fans do I need?
Three is the practical sweet spot for a mid tower: two front intakes and one rear exhaust. Adding a top exhaust helps with a hot graphics card. Beyond six, noise rises faster than cooling improves.
Should I run positive or negative pressure?
Slightly positive. Air then leaves through unfiltered gaps rather than entering through them, which dramatically reduces dust build-up for a negligible temperature cost.
Are 140mm fans better than 120mm?
At the same noise level, yes - a larger fan moves more air at a lower speed. The constraint is mounting points, since many cases and most radiators are designed around 120 mm.
Where should I mount an AIO radiator?
Top or front, with the tubes at the bottom of the pump. Front intake gives the CPU cooler air but warms everything downstream; top exhaust is kinder to the rest of the build and is usually the better choice.
Does cable management improve airflow?
Modestly, in modern cases with a separate cable channel - a few degrees at most. It matters far more in compact builds where cables genuinely block the airflow path.