How far is it from Charles de Gaulle airport in Paris to the Louvre and Orsay Museums?

You would have to take the RER and Metro which is cheaper will take you from 1-2hours to get there. Taxi 45min to 1 houur, but it will cost from anywhere from 60 to 80 euros.

The best way to travel to-and-fro in my opinion is by taxi. There are always tons and tons lined up in front of the airport to take you anywhere in or around Paris, just like any other airport. There is no reason to need to know directions, because the cad driver should and most likely will know how to get there. It would be much than say, renting a car for a day and having to figure out directions and parking. The cab ride to the museums may be a bit expensive, but its your most inexpensive choice. The museums are fairly close to eachother, about a 20 minute walk. Good luck!

Driving depending on traffic about an hour. Hire drive or taxi. Sorry don't know how far to the metro/tube, but probably the same length of time as driving. Orsay across the bridge over the seine, beautiful, enjoyed more than the louvre. You can do it in a day but you'll be exhausted and rushed. Why not consider a stop over.

Yes, they are very easy to get to. You can take the train. There is a train stop right there at the airport. And there is a train stop in between the Louvre & Orsay Museums (they are across the street from one another). I think you have to change trains, but not positive. We took the train to those museums from our hotel, so we took a different route. Still, very easy to get too. Make sure you get there early, and you may want to make a weekend out of it. Both museums are huge and you'll never see everything in 2 days, but you could make a decent dent.