Getting between CDG and central Paris...Le Bus?

We used LeBus last spring. We bought our tickets on line, ahead of time, and only had to wait about 7 or 8 minutes for the bus. We'll use LeBus again on our next trip to Paris.

Cannot attest to the regularity of service, but our trip on route #4 from CDG to Gare Montparnasse (early afternoon; Friday in September ) took 3 hours! Traffic just crawled and we were stuck in it:(. I would take the RER myself if timelinesss is important, you are at the mercy of traffic with the bus.

Le Bus Direct has always been a favorite for me, and can be a great resource for getting to the airport during a strike.

However the RER B train will get you close to the areas you mentioned, and with time at a premium I’d opt for it. The St Michel stop will put you right where you wanted to be. Connect to RER C train right there for a quick ride to the Eiffel Tower.
https://easycdg.com/rer-charles-de-gaulle-airport-cdg-to-paris-by-train/

Is there a reason you're not considering the RER B?

It would seem to be the obvious solution: as far as I can tell, you will not be laden down with heavy bags, and you are not specifically traveling to one of the destinations directly served by Le Bus Direct, such as Gare Montparnasse. It's also cheaper, at €17.80 a person for a round trip, and avoids any traffic issues, which probably wouldn't have been an issue when heading into the city but might be when heading back to the airport.

(€17.80 because if you are making a round-trip to/from the airport within one calendar day, the cheapest thing to do is to buy a 1-day zone 1-5 Mobilis ticket for €17.80 per person, which would include both your CDG-Paris RER trips as well as any metro or bus travel in Paris you may take. Compare buying two one-way tickets on the RER B, which would be €10.30 x 2 = €20.60 per person, plus cost of any Paris metro or bus travel.)

As for strikes, if the RER B is on strike (and as the person who did the translation of the daily transport updates for over a month, I can tell you there was service every day on the RER B from CDG to Paris, even if reduced), I would be quite conservative about heading into Paris on a layover by any means anyway -- traffic will be likely to be atrocious in that case.

I would also consider the RER B train which leaves from CDG and takes about 40 minutes to get to central Paris. You could get off at the Saint Michel-Notre Dame stop. The cost will be 10.30 euros per person each way.

On our last trip we took the RER B from the Luxembourg stop to the airport. It will be easy for you since you won't have most of your luggage.

Pay attention to what Andrew has said about the Mobilis five-zone pass. Very smart.

I agree that in your situation the RER is the best option into town. I really like the Bus Direct, but one of the lines goes into my neighborhood and it is a comfortable way for me to get into town and not have to worry about schlepping my luggage up and down metro steps (and it is more comfortable than the RER B which is a good thing since le Bus Direct definitely can get stuck in traffic, as someone mentioned above!) You don’t have that issue as you are traveling light — and if it’s a normal day when the RER is operating properly, it will be faster too. (Note that it’s not just strikes that slow down the RER B, it can also fall victim to mechanical issues or sick passengers, so you can never be 100% sure).

Hmm. We've done the RER B train before, although it was a few years ago so my memory of it is not fresh.

Price difference is not a big issue. Higher priority is being sure that we get where we need to be on time (most of all the trip back to the airport). Coming from the airport, it would be mid-day, and I assume traffic would not be bad. But returning to the airport, we would probably catch some rush hour traffic...which makes the RER B option (even if crowded, and filled with pickpockets) a safer choice. And if we are going to take the RER B train back, we might as well take it from the airport to the city too, so we have some practice and are familiar with the system when we will need to be on our A Game (returning to the airport).

I think you convinced me.

Another vote for Le Bus. We liked it because it was relatively painless, and we didn’t have to mess with the train, the seats are comfortable, and you can relax a bit into town.

You can buy right there, or just go on the web and buy in advance,

Personally I would choose the RER .. its not that bad.. its fast.. and it will take you right to the heart of Paris..

Been following along. Good info. We have been to Paris twice and used the Roissybus. This time we are dropping a rental car at CDG, staying in an airport hotel night before our early morning flight and would like to head into the city just for the last afternoon/evening so this info about the RER and the ‘day pass’ mentioned was very helpful.

A note: if you do end up purchasing the Mobilis day pass for zones 1-5, you need to write the DATE and your FIRST AND LAST NAMES in ink on the front of the ticket. If you don’t do that, they will fine you if they check tickets.

Also, when traveling on the RER, remember you have to use the ticket to EXIT the system in addition to when you enter the system.

We've taken both Le Bus and RER B over the years. I like Le Bus, but in your case I think the RER might be the best choice, given your time constraints, where you're going, the lack of luggage, and the time of day.