The mini-ITX computer will be a general use computer. Not a dedicated HTPC or Home server.

In general use mini-ITX cases, what PSU form factor is usually used? I understand that some case manufacturers provide custom built PSU to fit their case but I prefer to get the ones that use a PSU that follows standard form factors in case a replacement is needed.

For example, what PSU fits into general purpose cases by Lian Li?

Am I to assume that smaller PSU form factors also affect the possible maximum output?

3 Answers 3


Wikipedia says

The Mini-ITX standard does not define a standard for the power supply ...

Which means size and layout of PSU depends only on the case.

... though it makes some suggestions of possible options. Conventionally Mini-ITX boards use a 20- or 24-pin "original ATX" power connector. This is usually connected to a DC-DC converter board which in turn is connected to an external power adapter. Generally both the power adapter and the DC-DC board are supplied with the case.

An Intel document suggests

Provided the very different needs of the platforms that fit in the small desktop form category, this specification does not attempt to define a standard for the power supply to match with the Mini-ITX motherboard specification. Instead it recommends that manufacturers consider using a:

  • SFX, TFX or FlexATX are available power supply form factor for chassis greater than 5 liters
  • External power adapter for chassis less than 5 liters

P.S. Mini-ITX inside a PSU!

  • Yes, I understand that the application for mini-ITX computers varies wildly. Which is why I specified that this will be a general use computer. Cases vary as to what the application will be. For example, cases for HTPC will have a slimmer shape than general purpose cases. I'm more interested in knowing what form factor PSU general purpose cases use. But based on the shape alone, and the document you provided. I'm assuming SFX is preferred. This is good enough I guess. Nov 6, 2012 at 12:59

Most Lian Li mini-ITX uses standard ATX (PC-Q03, Q07, Q11, etc.) or SFX (PC-Q02, TU100).

The two popular SFX PSU that I know of both top out at 450W http://www.fspgroupusa.com/fsp45060ghs85r/p/858.html http://www.silverstonetek.com/product.php?pid=342 So I think it's safe to assume maximum output will be somewhat limited compared to standard ATX PSUs. That said, if you are using a mini-ITX case, chances are 450W will be enough.


You would typically need to go for an SFX Standard Power Supply for ITX Cases. These PSU's also include brackets for you to mount it on a Full-Size chassis. Typically they come in Gold and Bronze ratings and it should handle a mid-range Graphics card easily.

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