How many Days would I need in Italy to do the following in each city?

Rome: Colosseum, Trevi Fountain, St. Peters Basilica, Vatican City including Sisteen Chapel

You can do these in one day. But I would stay in Rome at least 3 days

Venice: St. Marks Square including St. Marks Basilica, Grande Canal, Rialto Bridge

You can do these all in one day. But I would stay in Venice at least 3 days

Florence: Uffizi Gallery, Cathedral of Santa Maria, Galleria dell'Academia

I'd break this up in 2 days but would stay in Florence at least 4 days if doing day trips.

Tuscany: Wine/Food Tour, Saturnia Hot Springs

2 separate days of day trips from Florence

Boat trip from Salerno to Capri with dinner on the Almafi Coast (where should I stay or take a train from to do this?)

You can do this in one day but I'd stay on the Amalfi Coast at least 3 days. There is a ferry from Salerno to Capri but you can take one from Sorrento, Positano, or Naples also. I'd stay in Sorrento in your case.

You can hit your Rome attractions in two days, but give yourself at least three full days in Rome to enjoy it and be able to wander the Eternal City. Try to get your Vatican museum ticket in advance for the hour the museums open.
Get timed tickets for opening time at the Uffizi Gallery. If you do that, you can actually see your attractions in Florence in a day. You could- not sure if you should. You could stay just outside Florence in Fiesole, or even take a 75 - minute express bus to Siena and stay there to see more of Tuscany. I trust you have a tour taking you to Saturnia Hot Springs as it’s not easily accessible by public transit
Again. for Venice you can see what you have on your list (so far) in a day. But, stay overnight at least, so you can experience Venice in the evening when all the day trippers have left. That’s when Venice is most magical.
You’ll do better staying in Sorrento to take a ferry to Capri — the ferry takes 20-30 minutes from Sorrento. Sorrento is also only a 30-minute train ride from Pompeii, so you can add that to your itinerary if you want to. Salerno is a grotty port town and an Italian Navy base. I would not stay there. Amalfi Town on the Amalfi Coast makes a nice base as it has ferry and bus service. The town next door, Atrani, is quieter than Amalfi.
If you want to save money on accommodations, you should start making cancellable reservations ASAP.
Italy is going to be very crowded with travelers this summer, and prices will only rise as time moves on.
Check www. trivago.com so you have an idea on pricing.
Have a great Trip!

I can't do that math but somewhere you should factor in some wow, what is that time! There's a whole lot more to each of those stops than just picking out TA's most popular things to do / see.

Absolute minimum:

Rome, 2 days. Vatican Museum/Sistine Chapel, St. Peter’s, Vatican City need one day just for that. For the Colosseum on the other day, be sure to do the underground tour, not just the above ground part.

Venice, 1 day to see those 3 things.

Florence, best to do in 2 days minimum. Could do in just one day if you made a very quickie stop at the Uffizi, and then at the Academia looked up at the statue and said, “Yep, that’s the David,” and then moved on to the church.

Tuscany, give yourself a minimum of 3 days.

We had a rental car, and stayed in Salerno one night, then Sorrento for several nights. Visited Capri (by boat) from Sorrento. Whether you used a boat or train from Salerno, would it allow a stop along the way back for dinner? What are the schedules, and prices? Maybe all that would influence your decision.

“Dolce far Niente!”
To experience Italy as Italians do, allow for time when there’s nothing scheduled- “ the sweetness of doing nothing.”

So you've taken the CT off the plate for the Amalfi instead?
Before diving in, I'll ask again what time of year you intend to take this trip?

Saturnia Hot Springs: have you researched how to get to this one? At a quick glance, it would be a real pain without a rental car, and it's not really close to anything else on your list. Just sayin' as I didn't have the feeling you intended to rent a vehicle at any point?

Rome: you mentioned in your other post that art (and food) were the goals on this trip? You really should add Galleria Borghese to your must-see list: IMHO, it's the best art museum in the city. There's a lot more to see in Florence as well.

For this trip you should fly into Venice and out of Rome.

Your order should be Venice>Florence (Tuscany day trip from there) > Amalfi Coast >Rome. If you intend to sightsee the Amalfi Coast, you should stay there. What, no Pompeii? Sure, you don't HAVE to do it but it's interesting that you've left it out as it's a very, very popular attraction for people staying in the Naples, Sorrentine/Amalfi Coasts region.

If you have 12 nights, this is what I'd do:
Venice: 2 nights/1.5 days
Florence: 4 nights/3.5 days (one-day wine tour out of the city; I've not included Saturnia) The art, the art, the art....
Amalfi Coast: 3 nights/2.5 days
Rome: 3 nights/2.5 days. I sure would like to add another one to this for some more explorations time,. As your Colosseum ticket includes the Palatine and Forum, I'd recommend doing those. You should also see the Pantheon.

You might want to consider staying elsewhere on the coast than Salerno if Capri is on your list? It's a 2-hour haul by high-speed ferry to the island from there, and same going back. Right now, the first ferry leaves Salerno at 7:30 AM, and the last leaves Capri for Salerno at 5:15 PM. This route is also seasonal, meaning the boats don't run it in the winter months (Nov. through March), which is one of the reasons I'm asking when you're thinking of taking the trip.

Budget? I'm no good at figuring budgets for other folks but I'm sure someone else might be able to throw some figures at it. Rates tend to be lower during the winter months.

Thank you all. And yes I took off CT and want to spend just 1 day to do a boat tour and maybe dinner. All this information is great. I am trying to decide how much time I need to take off work with what we're wanting to do.

FOMO is a term tourists need to know - fear of missing out. You want it all. We all do, but too many places do not make a great trip. They make a rushed trip.

We've been to Europe as a couple 8 times. We have learned that less is more. We spent 3 nights in Chartres, where most spend 1 night or do it as a day trip. We remember the stay fondly - we went to several local restaurants, did a picnic, saw the Cathedral, walked around a lot.

Better to have a smaller trip than a trip visiting a lot of cities. In Sept-Oct, we will stay about 6 nights in Milan, Turin, and Florence. We will do day trips to other nearby places. We will unpack/pack 3 times. We will not see Rome, Naples, Amalfi Coast, Cinco Terre, Venice. There's so much in N Italy that S Italy is not important. We may never go to S Italy. That's OK.

Kenko and Paul make excellent points. If you've never been to Italy and don't know if you'll ever return, FOMO can be a powerful force.

We've traveled on "If it's Tuesday, It Must Be Belgium" type trips but now have slowed down. We've been to Paris twice in the last 5 years and neither time visited the Eiffel Tower or the Louvre. We spent a week in the French countryside and spent just one day visiting the region's chateaux. We did the same for 10 days in Tuscany, staying at an agriturismo with only one day in Florence.

Also, be sure to factor in travel times. By trying to go to so many places, you'll burn up a lot of time moving from one place to another.

If you stay in Florence more than one day(and if you're an art lover, you should), the Museo San Marco in Florence is a rare opportunity to see art in its original setting, in this case, a monastery.

I like to count nights on the ground rather than days.
Rome: 3 nights (2 full days) are enough to cover your list. A minimum of 4 nights is however what I consider ideal for Rome.
Venice: 2 nights (one full day) is enough to cover your list. A minimum of 3 nights is however what I consider ideal for Venice because it would give you a chance to visit the lagoon islands, like Murano (glass blowing), Burano (colorful facades and laces), Torcello (Abbey).
Florence: 2 nights (one full day) is probably enough to cover your short list (busy day though). However I would consider at least 3 nights more appropriate to see the basics of Florence, because there is much more that can be added to the list in Florence alone. If you are also interested in taking day trips to other Tuscan locations (Florence is a great base for Tuscany) then you need an extra night for each day trip you plan to take. Florence is the capital of Tuscany, for some reason many Americans think Florence is not in Tuscany.
Tuscany: The Chianti area, Tuscany’s most famous wine region can be visited from Florence on a day trip. It’s only 20-60 min from Florence (depending on where in the Chianti). The Terme di Saturnia are in southern Tuscany and probably closer to Rome than Florence (a couple of hour drive from each). If you are interested in going I would spend at least one night in the area. I have driven from my house in Florence to Saturnia and back just for the day, but it was a long day. After a few hours soaking in the thermal waters driving back home to Florence was a pain, I almost fell asleep at the wheel. If you don’t have a car, I don’t think it’s possible to do it at all from Florence on a day trip.
Amalfi Coast. You can stay two nights (one full day) on the Amalfi coast or Sorrento and do what you mentioned. However I consider a minimum of 3-4 night ideal for this area because it gives you a chance to add other places to house short list, such as Naples, Pompeii, Ercolano, and even Procida and Ischia.

... want to spend just 1 day to do a boat tour and maybe dinner

Jennifer, I personally don't consider the Amalfi Coast a day trip from Rome, and not a 1-nighter either. Do consider that the weather isn't perfect there ALL the time, and that the single day you allotted for it might be a wet one. Really, I'd save the coast for a future trip when you can give it the 3-4 nights it deserves. There is enough to see in that region for that sort of time, and you'd have some flexibility to work around the weather should you encounter a stormy day.

You also mentioned in a PM that you were weighing doing this trip in either October or Dec.? Even if you had the time, I wouldn't do either the CT or the Amalfi coast in winter (Dec.) when the ferries either aren't running at all (CT) or very minimally so (A.C.) and many businesses close for the season. Rough seas can also be boat-tour complication.

Good advice from Paul and others about FOMO: it's all too easy to try and cram too much into too little and end up spending too much valuable sightseeing time dealing with transport and changing hotels (which can take more time than you think it can).

Florence is a really good base for day trips around the greater Tuscan region, as Roberto mentioned regarding the Chianti wine area. Additionally, oodles of RS posters have done Siena, Lucca, Pisa, Fiesole and some other locations from Firenze. It can be freeing to just jump on a train (or bus, in some cases) without having to deal with the luggage! Fewer hotels to have to research and book, too. :O)

Cala recommended Museo San Marco in Florence for art lovers like yourselves? Absolutely. The city's Renaissance treasures don't begin and end with the Uffizi and Accademia. Also, the Italian National Museums are closed on Mondays in all Italian cities so you want to be careful to work around that. You might find the duomo's museum and baptistry to be more interesting than the interior of the church itself? It's surprisingly austere compared to the intricate polychrome exterior. There are other Florentine churches that I'd put in the to-do list before that one, especially as it often involves a long, long queue to get in.

What month is the best to visit the Almafi Coast? What months have the least rain?

Any suggestions you recommend that are better than the list I have I am all for it! I can switch out things to do when we are there for a better experience.

You never mentioned the length of your trip. If you are there for 6 weeks, that's one thing, but a 2 week trip is very different. What's your trip length?

Correct I haven't because I'm trying to find the minimum number of days for the activities that I have listed. My goal is to see the least amount of time I need to take off work. Hoping to accomplish all this in 2 weeks or less.

If you have 2 weeks, I would consider Florence and Rome and Tuscany. Adding stops like Venice and Naples is just going to be rushed. Have you read the Rick Steves Italy book on these locations? But of course, it's your trip.

In Sept, we go to Italy. Our trip is
Days
1-6 Milan and side trips
7-11 Turin - Food and Wine Festival
12-20 Florence and side trips

We won't be going to Rome, Venice, Naples, or the Cinco Terre. We enjoy have a base and unpacking 1 time for 4-5 days. Now, we are much more experienced travelers in our 70s. You are probably in your 30s, and off to Europe for the first time. You have a different agenda than we do.

Jennifer, if you can take 2 weeks off work, I think you can have 13 nights to work with?. I'm pushing the envelope here as airfare is expensive so you want to get as much good out of the getting there as possible, and see MORE than the minimum while you're there. We'd come up with some additional stuff that wasn't on your list, like the Borghese, but which fit your art/wine tour/general pretty surroundings interest, right? Just IMHO.

So, if you can leave on a Saturday and fly over night, you'll arrive on a Sunday and have 1/2 of a jet-lagged day to get yourself onto Italy time. Leave on a Saturday two weeks later, get home on the same Saturday, and you can add another night to Rome + have Sunday to recover before work on Monday.

Venice: 2 nights/1.5 days (Sun/Mon)
Florence: 4 nights/3.5 days (one-day wine tour out of the city) Tues/Wed/Thurs/Fri,
Amalfi Coast: 3 nights/2.5 days Sat/Sun/Mon
Rome: 4 nights/3.5 days. Tues/Wed/Thurs/Fri.

Driest AC season is summer... when it's hot (especially in Rome, Florence and some other areas), the area is teeming with tourists, accommodation prices tend to be at peak, and public transport is very busy. But weather is always a crapshoot any way you shake it; we've been rained/flash-flooded out of some typically very dry hiking spots in the US so averages don't always work as they're supposed to. Multiple days will give you at least more than one shot at a dry one, though.

If keeping 3 nights/2.5 days, it is possible to do Pompei en route to Sorrento...which is where I'd stay if planning to day-trip by ferry to Capri. Coming from Florence, you would change trains in Naples to the local Circumvesuviana commuter. It stops at Pompei Scavi-Villa dei Misteri station right, in front of the main entrance to the scavi, and the route ends in Sorrento. It's battered and worn but cheap and gets the job done. There is luggage storage at the train station or at the archeological site itself.