I have recently qualified with PADI to use a Drysuit to dive in cold water. In order to submit the paperwork the dive company I took the course with require a couple of passport sized photographs.
I wanted to know what the dimensions were for a "passport sized photo" and hence searched via my web browser. I came across an excellent article titled Make your own passport photos which nearly gave me what I was looking for - it told me that I needed an image 4.5cm high and 3.5cm wide - the trouble was they used a Photoshop to resize the image and I don't have a copy of it. So I wondered what software I already had that could do the job for me.
The first place I looked was Microsoft Office Picture Manager as it's built into Microsoft Office and I've used it for years for most of my photo editing - it's not particularly sophisticated but it's easy to use and very effective. Sadly for me it can only resize in terms of how many pixels or percentage of the original size.
I quickly found the easy way to resize the image in cm (or mm) - use Microsoft Word 2007. The following screenshot shows what happened when I hit "insert picture" - the useful part is in the top right hand corner.
Of course if this picture was for a UK passport then it would be rejected as I wouldn't be allowed to smile!