Dimensions of a power supply

[Adaman123]

Hi, I have a pre-built computer that I wanted to upgrade to a r9 290 but my power supply (450w) won't handle it. I also have a micro atx case and I can't find a power supply (550w to 650w). I checked the dimensions of a power supply and it says
Item Dimensions L x W x H 5.51 x 5.91 x 3.35 inches
And I have a question, the width would be which side of the power supply? the side that goes into the back of the pc of the side that you see through the side.
Please help.

 

[Spu7nik]

The width should be the side that you can see through the back, if I'm not mistaking (ie. the side with the power switch, AC, etc...).

http://www.nextdayturf.co.uk/images/page/length-width-depth-rectangle.jpg

 

[misteriosly]

http://www.atxpowersupplies.com/images/430wps-pic.gif
Depth=Length