Unfortunately, the format used in IS/MS isn't strictly decimal or degrees/minutes/seconds, but a hybrid of the two; so that site won't help much, although it has been very useful for me for other purposes.
All you're really doing is using a calculator to divide the seconds by 60 and tacking the result on to the end of the minutes.
I have a shortcut to the Windows calculator on my quick-launch toolbar so I can do calculations like this quickly.