Chambord and Chenonceau same day after travel

Too much for one day. Chenonceau is lot more crowded since it is smaller. I have not driven that route but looking at how far it is on the map
I would split it up.

Chambord is somewhat underwhelming. I loved Chenonceau.

And I thought Chambord is more spectacular from the outside. I have a picture I took in front of it across the moat that always get a wow! whenever people see it

We did both of those Chateaux on the same day, but we started out locally early in the morning. You have a 3.5 + hr drive (in ideal conditions) to start the day, so you wouldn't even get to Chambord til noon. Then you need lunch. Figure 2-3 hours to tour the palace and grounds. It's now 3-4 pm. It's an hour+ drive to Chenenceau. Then you have to park and walk to the Chateau. And while it is one of the smaller chateaux, it is such a jewel box that you do it a disservice to rush through it and/or lack the time to view the surrounding gardens. So, it's possible to do both in your scenario, but it will be rushed, and you'll likely be exhausted after a very long day.

I agree that the drive from MSM makes the day too long. But I wanted to add that we visited Chenonceaux first thing in the morning and it was practically empty (in July!). Chambord is much bigger, or felt bigger, so while there were far more people there when we went than had been at Chenonceaux, it still felt un-crowded.

Think it will be too much, but you can drive first to Château de Chenonceau and decide there if you still have the time or energy for going to Chambord and back to Chenonceaux. For the latter means driving along local roads, with trucks, tractors and sometimes speed limits of 30 km/h you will need more time as your route planner calculate. I would keep Chambord for another day and follow a scenic route along the Loire river for instance.

The outside of Chambord is anyway worth to see and very impressive, you can make a detour if driving to Chartres / Paris later in case your time is too limited for a seperate visit.

No, this isn’t feasible. You are severely underestimating the length of all these drives.

I would also recommend driving Mont St Michel to Chenonceau, visiting there, and then deciding if I really wanted to visit Chambord. I find the best bit of Chambord is the view of the exterior, so it can easily be done as a driveby.

Allow at least 3 hours for the drive south, more if you take a route where you might see something. That Autoroute is one of the worlds most boring roads. I would travel via Fougeres, Mayenne and Montoire sur loir

It's not a precise comment, but we found that the attractions towards MSM (Fougeres, Vitre, etc.) were farther from the highway (say, 20 minutes each way) than they are in the Loire. In that sense, it is not always realistic to think of lovely stopovers during a long drive. While Google Maps times are imprecise, I find that adding 15% works out well enough.

I agree with others who say too much. I also suggest checking closing times of Chenonceau.

We were there two weeks ago, arriving around 1:30-2:00. It was fairly crowded, but not bad. The crowd peaked about 3:00-3:30. We left about 5:00. Around 4:30, the crowds started to drop off quickly. Chenonceau Was open until 7:00. I would choose to go either first thing or late in the afternoon when the tour buses have left.

This day is not going to be tough. It is almost a 5-hour drive from Mont Saint-Michel to Chateau Chambord and then a 1-hour (maybe even 1.5-hour drive) between the chateaux. If by see you mean a drive-by, which would probably be okay at Chambord unless you want to see the spiral staircase (some rooms are basically empty), you could maybe do this day.

We went to Chenonceau around 5 in June 2015 and it was wonderful-so quiet and peaceful,