Ideally, you should spend 3 days in Venice
Venice is simply breathtaking whether you have 1 day or 5 days. While 3 days is a perfect visit to Venice, you can easily modify your itinerary with these practical suggestions:
1 day in Venice
Spend most of the day in and around the attractions of St.Mark’s square. Also possibly have time to visit Rialto bridge, or San Giorgio Maggiore across the lagoon.
2 days in Venice
Most of one day in St. Mark’s Square, ride the vaporetto up and down Grand Canal, visit one of the other islands, have a nice local meal.
3 days in Venice
See all the major attractions (Basilica, Doge’s Palace, Guggenheim Museum, Accademia), see the main bridges of Venice, go on a islands visit, take a walking tour of the interiors of Venice, discover less touristy parts of Venice.
4 days in Venice
Spend more time at each attraction and take custom tours to understand the stories. Spend an entire day at the Burano, Murano, and Torcello. Visit Lido island, San Giorgio Maggiore, and the main local markets.
5 days in Venice
Spend half your time on the sights and the rest of your time wandering and discovering. It is probably too long to spend 5 days in Venice unless you are here without an agenda.
Venice is one of those cities that you might never want to leave once you get there, so it is important to plan your trip in a way that you get to do everything you have planned, as well as appreciating the city for what it is. Here is an outline of what you could expect for the number of days you have planned in Venice:
One day - Very packed
If you only have one day in Venice, you will probably not be able to appreciate all that it has to offer. You would have time to visit the main sights in Saint Mark's Square, cross the Rialto bridge (or maybe go under it in a water bus or gondola), visit the Rialto market, and probably have time for a romantic gondola ride if you are staying until the evening.
Two days - Some major sights and some discovery
If you have two days, you would be able to tick off all the major sights on the first day, and then cruise the second day. Often one of the best parts about visiting Venice is just walking and getting lost. On the second day you could make a day of visiting the back streets, going on a secret wine tour to learn how to drink like a local, go to the Viva Vivaldi exhibition, go to some of the lesser known churches and go have time to appreciate the art galleries like Peggy Guggenheim's collection and the Accademia. This is a city for getting lost in, for drinking wine in, and for trying out the local cuisine while you look out over the canals.
Three days - Perfect balance of sights and off beat activities
If you have three days, you would easily be able to visit some of the many surrounding islands around the main island of Venice. With an extra day, you could visit the islands of Murano, Burano and Torcello, which all offer an escape from some of the ever-present crowds in the centre of Venice and give a different perspective on Venetian life. If you have three days, this would probably be better suited to the second day so that you are not rushing to get back if you need to catch transport out of the city. By day three you will probably want to chill out, and you might have more bearings so you could wander and get lost without getting hopelessly lost
Day 1: Saint Mark's Cathedral, Saint Mark's Bell Tower, Doge's Palace, Rialto Bridge, Rialto Market, Gondola Ride, Cruise down the Grand Canal on the public transport system
Day 2: Visit Murano with its glass blowing, Visit Burano with its picturesque colourful houses and fresh fish market, Visit Torcello with its quiet beauty, rose gardens, and church with a lookout
Day 3: Chill out and get lost in the streets of Venice! Go and see the more well-known art galleries, and take a wine and food tour through the back streets
More than three days
If you have more than three days (which would be wonderful) you can do all of these things but at more of your own pace. Obviously you can fit more in if you are wanting to cram everything in, but Venice is a city for walking and wandering and discovering, so planning for at least three days will give you a good opportunity to connect with the city, and more than three days will give you space to chill and maybe take a few more days trips.
Minimum two nights:
The first day - I would spend it to visit and see the main sights and attractions of Venice, such as the Rialto Bridge, Piazza San Marco, the Zattere foundation, the Frari basilica ... making stops in the typical taverns and bacari for enjoy and drink typical dishes and drinks.
On the second day - I would use it by moving on a vaporetto, with a daily pass, to see Venice from the water: the most prestigious facades of the buildings in fact give the canal, being Venice a city thought in antiquity to be traveled by boat.
Also with the same subscription you can reach the other beautiful islands of the lagoon like Murano, Burano, Torcello, Lido, Giudecca ...
On the third day - I would use it to see one of the countless exhibitions or museums that the city offers, visit a place that I'm particularly interested or simply walking around, losing myself in the maze of Venetian alleys. I, after almost ten years living here, sometimes I get lost and discover new places in the city: I find this a wonderful thing!