What would be the best way to get from St Paul metro station to CDG airport? Would it be best to take metro to Gare Du Nord, or Les Halles and then take RER Line B? If we have a Saturday flight out at 9am, what time should we start out, and do we need a ticket different than the Metro tickets we would be using in Paris all week?
I think it would more direct to take line 1 from St Paul to Chatelet then RER B to CDG. I believe you have to buy a RER ticket once at Chatelet. This is helpful link:
http://parisbytrain.com/
If you take metro line 1 to Chatelet and walk through the tunnels to the Chatelet-Les Halles RER station, you'll only have to make one connection. To get from Saint Paul to CDG via Gare du Nord would require a connection at Bastille as well as Gare du Nord. Sincle tickets from anywhre in central Paris to CDG cost €8.70 and include unlimited transfers on the metro and RER. Buy your tickets at Saint Paul. However, you should be aware that it is wise to be at CDG a full three hours before a flight across the Atlantic. The metro doesn't start running early enough for you to do that. The first line 1 train you could take leaves Saint Paul at 05:39; connecting at Chatelet-Les Halles will get you to CDG at 06:29. If you take a taxi to Gare du Nord, you can catch the first RER B train which leaves at 04:57 and arrives at CDG at 05:27. Or depart at 05:29 and arrive at 05:58.