Is this doable?

Why St Gallen?
It is a semi-industrial town. Not the first place I would think of for a one-day visit to Switzerland.
I think you mean Salzburg!

I would recommend Lindau (look it up). Then over the Arlberg Pass via Innsbruck to Salzburg.
Do-able, but I would strongly recommend you allow some more nights for this, and after Lindau go properly into the Swiss Alps for 2+ nigjts.

I loved St. Gallen. The old abbey library is a gem, and the books on exposition are incredible. As I saw a 10th century Graduale (the book of Mass chants) I began to weep.
The drive between St. Gallen and Salzburg is on the longish side. 4 hours looks optimistic to me. As much as I love Salzburg, I would stop in Innsbruck - taking out two hours from the drive - and have some more time to look around.

Hi Joseph. It would help us answer if you explained why you want to go to Switzerland. If you are looking for scenic mountains, there are many of those in Austria, and would be more practical in connection with Salzburg. Enjoy your trip!

If you don't want to purchase a Swiss or Austrian vignette, it will take an extra hour to St Gallen because you can't use the superhighways in Austria or Switzerland. Going to Salzburg, you would also add an hour and need to use the route back to Munich. If you want to use the route over the Arlberg pass and the Inn valley, it will take an hour longer and you definitely need an Austrian vignette.

The Swiss vignette is 40 CHF, and a 10-day Austrian vignette is 8.90 EUR, A compromise might be to get the Austrian vignette, since it pretty inexpensive, and stay off any Swiss motorways. If you just want to make time, buy both. And you will also have to add the time to buy these at the borders and attach them to you windshield. Finally, traffic delays could mess with your google estimates.

That is a lot of driving imo. I do not know your age but i limit my driving to 2 hrs per day max. It is tiring and u do want to enjoy your time when visiting. Have u thought of train travel? Or perhaps somewhere closer to Munich.

I will be 70 then. Now I easily drive for 6 hours at a time, so I am used to driving. I am embarrassed to say why I want to hit Switzerland, and in particular St Gallen. About thirty years ago I visited San Francisco and bought a "new" type cup of coffee and enjoyed it. As a memento, I bought a coffee mug to remember that odd new coffee shop called Starbucks. Since then, whenever I visit a city or country, I buy a Starbucks mug as a reminder. St Gallen is one of the few Starbucks locations in Switzerland and is the closest to Munich.

Over the years I have built quite a collection of these mugs. Don't get me wrong, I will go there for the mug, but seek my espresso at a local, independent coffee shop.

Yeah it is strange, but much better than buying a new puppy in every big city or country I visit. (This is my excuse to the Warden and I'm stickin to it!)

Hi Joseph:

I love your reason to go to Switzerland. On one of my RS tours there were two women who collected the Starbucks travel mugs in every city they went to. Her husband was joking that they had to get up really early on the day they left Paris so they could buy the mug before they left to start the tour!

I collect yarn when I travel. On one tour, I was helped out by my tour mates and it became a sort of scavenger hunt to find a yarn store. Yes we found some in Baune.

I say go get that mug if that is what you want.

Appenzell is a lovely, smaller town near St. Gallen and at the base of a mountain lift. It doesn't get you any closer to Salzburg but is a worthwhile destination in itself.

Google claims it is a 2:27 minute drive

Google is way too optimistic. In my experience, you always have to add approx. 30%. Munich - Lindau (at the austrian border) takes normally 2 hours and from there to St Gallen it's at least another hour. And then you have to add to the driving time the stops for queuing up at the single Austrian counter for buying the motorway sticker (there is no filling station on the Memmingen - Lindau motorway where it would be available) and at the Swiss border for the swiss toll sticker. After Bregenz you will have to cut through the crowded town of Lustenau to get to the swiss autobahn (there is no corridor between the Austrian and the Swiss autobahn networks), which gives great prospects for a decent stau. On your way to Salzburg you will have to go along the infamous Rosenheim - Salzburg autobahn leg which is stau prone all the time. So, I'd include in my calculations a thick time cushion. All the better if everything goes smooth.

sla019, thanks for the tip. When adding the Google times, it is a half hour shorter driving St Gallen to Salzburg than it would be driving back to Munich, staying at our hotel then driving to Salzburg the next day. Adding your 30% cushion, it appears to be a seven hour round trip, Munich to St Gallen, and a four hour round trip, Munich to Salzburg.

I regularly take a six hour drive to my cabin so these times will not be a problem for me.

Again, it is all about what the weather is like and how I feel that day dependent.

Like Barbara, I absolutely love your reason for going to St. Gallen! Enjoy the trip!