Free travel in Paris from Charles-de-Gaulle airport and Paris Gare-du-Nord

No matter what kind of Eurail pass you have, using it to get from CDG to Gare du Nord will use one pass day. Unless you're going to take a fairly long train ride from Paris to another city on the same day as you arrive at CDG, don't waste a pass day. €8.40 will buy you a ticket on the RER B to Paris and it includes unlimited transfers to other RER lines and/or Metro lines until you exit the system, thus getting you to within a few blocks of any hotel in Paris.

Thanks Tim!

how does that work if you have a global pass,since the pass allows for unlimited travel. som if i wanted to use a train that day what happens?

If you have a global pass consecutive, then go ahead and save a few euros by using the pass for the ride from CDG to Paris. Exception: Unless you don't need all the days from the start to the finish of your consecutive period, I wouldn't use the pass if that would be the first day you use it and it's the only ride you would take that day. Wait to validate and use it when you take your first ride on a regular SNCF train so your consecutive day period will begin then.

If you have a global pass flexi and aren't taking any other long train rides that day, I certainly wouldn't waste a pass day to get from CDG to Paris.