The converter i use on my iPhone is:
Coordinates Converter v2
by: MASAMA Inc.
It works very well, when i am away from home and can't use BaseCamp.
I use it when i get coordinates from Google map and want to put them in my Garmin GPS.
There needs to be a basic understanding of the systems.
Here are the 3 basic systems. There are more....
In the old days..... using paper maps, we used Degrees, Minutes and Seconds (DMS)
Eg: N25deg 30' 00" E055deg 15' 00"
Here, each degree is split into 60 minutes and each minute is split into 60 seconds.
It is similar to an analog watch, where 06h30 is half past six.
Please note, I cant seem to write the deg correctly, it should be written as a small circle in the same place the ' and " are shown.
Most importantly, you can forget this system, It is not really useful for us.
Google map uses a decimal system (D.d)
Eg: N25.50000 E055.25000
This has the degree split by the conventional decimal system.
So in the example above it is N25 and a half / E055 and a quarter
most people set there Garmin GPS to use Degree and Minutes with decimal minutes (DM.m)
Eg: N25 30.000 E055 15.000
Here, each degree is split into 60 minutes and each minute is split by the conventional decimal system.
In the examples above, all three systems are giving the same point.
When converting between the systems, the BIG thing to remember is to do a quick "gross error" check.
I will give an example:
N25.50000 E055.25000 on Google is very far away from N25 50.000 E055 25.000, that you may be tempted to put in your GPS.
Hope this helps someone.....