I use DD.ddddd ,sometime back i read that it was the most accurate. But I don't know if it is. Most programs will automatically convert them. after they are all entered in the format that they are,go to the properties,or preferences,or options tab,where ever you find the option to set the waypoint format and select the one you want or need.All the past entered will be converted to your new choice. I have no Idea how accurate the conversion is. There may also be some on line converters.