Several different ways to circulate around Paris exists. Here are some app to help you !
If there was only one app to have in your pocket, it might be this one : CityMapper. The holy bible of the Parisian transportation network : bus, subway, RER, Transilien, train, tram, Vélib’, taxis, everything’s on it. And on top of that, it also indicates you whereas you should hop in front or in the back of the train, the number of calories burned, amongst other thing ! Download on Google Play or App Store