Reduce large font sizes in KDE

Are you, like me, surprised and annoyed over the large fonts when running KDE, read on I have come up with the solution.

Maybe you found that running KDE setup tool allows you to adjust the font from default 10 pt to 7 pt to make a more appropriate font size. This was what I did. Then you run Firefox, Eclipse or some other software not made by KDE and found, like me, that here the font is large, not saying huge. This made me wonder and trying to google a solution.

I found this idea; append -- -dpi 75 after the call to startx. True, this solves the problem but where should you enter this command to make it start automatically. Personally I can handle going to runlevel 3 and then manually type startx -- -dpi 75 and start working; hell I prefere it like that. My wife and children on the otherhand are'nt as console loving as I. Here is what I did.

After googling for a good two days I altered the xorg.conf file manually and changed this in Section Monitor:
DisplaySize 370 230 --> DisplaySize 677 423
How on earth did you come up with those figures you may wonder; well I simply took the x and y resolution of my monitor which is 1920x1200, divided each value by my preferred dpi which is 72. This brings me:
1920 / 72 = 26.67"
1200 / 72 = 16.67"
Since display size is in millimeter I multiplied this with 25.4:
1920 / 72 * 25.4 = 677.33
1200 / 72 * 25.4 = 423.33

Problem solved!