I'm planning a trip accross france this summer with a couple of friends, but I don't have any experience riding around in mountains, so I'm not sure how much time to budget for a section of an upcoming trip accross France.
That section is about 300km (186 miles).
For the rest of the trip we're planning on averaging 100km (62 miles) per day, so if it was flatish, i'd budget about 3 days of riding. I'm going to be the slowest person, and I'm not a great hill climber, and i'm also somewhat heavy, me + bike + stuff = ~300 pounds. On a superflat route I think i'd probably average 25km/h (15mph). I'm not expecting a perfect answer, just some ideas of how much slower the riding will be.