How do you know how much time it takes to get from one place to the other on the metro? For example, I have to go to Jules Joffrin from the Republique station. I need to be at the Jules Joffrin station about 8:45am.
Thats a bit complicated, you should walk to Simplon, ,then take line 4 to Gare du Nord, and transfer to line 5 to Republic,,, it will take you about 1/2 hour . Have you looked at taking a bus, it still means a transfer and 1/2 hour.. its just you are in a bit out of the way area .. I personally would leave about by 8 o'clock just to be safe. A taxi would only be 10-15 euros, if you have luggage you may wish to consider that instead.
Liz if you go to the Paris metro website (RATP.fr) and click on the little English flag up in the top right-hand corner, you'll get to a page where one of the choices is "Traveling.". Click on that and it will take you through to a page where you can input the names of the stations to see how long it will take. Remember service is less frequent on Sundays and holidays, and during the month of August (not sure when you need to make this trip).
I'll be doing this on a Saturday in September. Taxi sounds like an easier way to go. I'll check out that web site though because I have other trips to make.
I figure about 5-min per stop. So, count the stations between your start and finish and multiply that by 5 to get the approximate time the trip will take.