Google gps conversion..... there is a heap of sites on the web.
http://www.gpscoordinates.eu/convert-gps-coordinates.php

What are you trying to do?

 I've had this drama before and found the web conversions confusiong. 

Usually your plotter/GPS will have the option to change the format. So what you do is change it to the bottom format, enter all your points, and the change it back to the top format. The GPS should do the hard work for you. 

Fyi i had to do this with a garmin e trex handheld because I couldn't figure out how to do it with my lowrance plotter

The third calculator down on this page converts Degrees and Minutes to Degrees, Minutes and Seconds. Is that what your after?

If you want to change them all in bulk then probably try Sstevee's method.

http://www.csgnetwork.com/gpscoordconv.html

S91°00.2200'
E335°17.2500'

19.01.1310S
149.25.9750E

The formats are the same? Degrees, minutes, decimal minutes.

with u on that one starbug cant see the difference except the easting and northing is in front of the one set and behind the other

barcrusher if u wanna convert from deg,min'sec" to decimal format a scientific calculator is the easiest way (so 1degree30min would become 1.5degrees)

on the casio for instance u press deg followed by degree min sec button (looks like this °'") then minutes press button then seconds press button and it will display the decimal format or manually using normal maths use the degrees as full degrees, so write it down as it is, then times the minutes by 100 and divide by 60 write it down and do the same for the seconds ( x100/60 or u can divide60x100) from decimal format to minutes seconds x60 /100 hope this helps -if u cant follow the explanation - go to the local high school ask to see the math teacher -give him a six pack- he might get his clas of students to do all the conversions for u--DONT tell him its fishing spots