Milan-Paris is about 9 hours, travelling via Zurich, Geneva or Basel. If you’re travelling after Spring next year, you may be able to use the direct trains (they’re currently suspended due to a landslide).

Paris-Vienna will take you 11 hours or more, via Germany. Three times a week, there’s a direct night train.

Vienna-Milan will also take you a full day. Again, there’s a nightly direct sleeper train.

First I would check prices of regular tickets for each of your three journeys. Try raileurope.com for prices.

Then compare the cost of passes + compulsory reservations. This page gives good details of reservation costs. https://www.seat61.com/interrail-and-eurail-reservations.htm

Thanks for the reply. Unfortunately individually the trains cost more than the pass but my doubt is how to work out how many travel days to do if I don't know if there is availability on the train I want to take. Paris-Vienna there's the direct but I can't work out if it's still available or not, and if I then have to take a change and put in two days travel instead of one

The minimum pass you can buy is valid for 4 travel days, so you will have a spare day.

When are you travelling? Most of those trains - at least the daytime ones - aren’t what I’d call high risk of being fully sold out. And there is more than one route option for most of your itinerary. The sleeper trains do sell out, but with enough notice you should be able to secure a reservation.

I would have no hesitation in buying a 4 days in one month pass for those journeys.

Eh, at the end of this month, that’s way im a bit afary. But thak you for the answer and the advice

The pass could be good value then because the end of December is always quite busy. In fact, you should check availability now, especially for night trains, before buying a pass.

As for the Paris-Vienna and Vienna-Brescia routes, there should still be room because even the OBB website makes me buy tickets, but the Brescia-Paris route doesn't have a direct train, I would have to change at Ginevre and stay 6 hours in the station. Do you know if there are any resting rooms?

Please mention exact travel date and preferred departure times for exact travel advice from our side in this case. A 6 hour stopover seems quite long for that route.

I would leave Brescia at 6:09 p.m. with Eurocity EC 46 to Geneva (Switzerland) on 29/12, and then at 6:29 a.m. on 30/12 I would have the other train (TGV 9760 TGV Duplex Lyria) to Paris.  Or at least, this is the option that the website gives me with the least amount of stopovers.

With 2 stopovers you can do something much better (and not requiring 2 pass days). You shouldn't be afraid of connections, they're frequent especially in Switzerland. Simply plan some margin as ECs from Italy are usually late.

For example via Geneva:

- R Brescia - Milano Centrale 06:28 - 07:35

- EC Milano Centrale - Geneva 08:10 - 12:31 13€

- TGV Geneva - Paris Gare de Lyon 14:30 - 17:42 29€ reservation

To save money: take a TER to Bellegarde at 13:30 and board the TGV there (10€). 1h break in Geneva to buy food and 1h in Bellegarde to eat it. :)

Second example via the Gotthard route:

- R Brescia - Milano Centrale

- RE Milano Centrale - Lugano 10:43 - 11:58

- EC Lugano - Basel SBB 12:02 - 14:56 (or 12:30 - 15:28)

- break

- TGV Basel SBB - Paris Gare de Lyon 16:34 - 19:38 29€

Same way to save money: TER to Mulhouse or Strasbourg and TGV from there.

Thank you so much!
But so in this house, even if I take multiple trains because I have multiple changes, the travel day is one?

Sure, on a travel day, you can use as many trains as you want.

Ok thank you!!