SITA Bus from Sorrento to Ravello

The trip from Sorrento to Ravello will take about 1 12 hours. Transfer in Amalfi for the ride to Ravello.

Schedule, prices and bus info here.

http://www.positano.com/en/bus-schedule

3 day ticket will be your best bet.

You will have to take 2 buses:
1. From Sorrento to Amalfi
2. From Amalfi up to Ravello

You have links to SITA bus schedule and everything you need to know here: http://www.ravello.com/how-to-get-to-ravello/#FromSorrento

You buy your ticket (1 ride, 1 day or 3 days) at a tabac or other outlet in Sorrento, not in advance online. Unfortunately, these are all open seating local buses, so holding a ticket does not necessarily guarantee a place or a seat on a particular bus. Often at busy times seats are full and many people are standing. Also, often there can be so many people standing in line for a bus, that not all get on, and people need to stay in line for the next bus. So, especially at busy times in busy seasons, the "bus experience" can take you considerably longer than the time you spend actually on a moving bus.

Larry has summarized the negatives well and they are true depending on the crowds at the time.
The pluses are it is insanely easy, there really is only one main road and only one way to go, you will also not be alone taking the bus so given the fact you are asking the question now means you will be guiding dozens of others when you are there.

There are not that many stops at all and you will be getting off the end of the ride in Amalfi and then back on a bus that only makes one stop essentially a frequent shuttle between Amalfi and Ravello.

It is also a beautifully scenic drive! So by no means did I come away with a negative impression of my bus experiences both from Sorrento to Amalfi and Amalfi to Ravello.
If you are not in a rush and a bus is near full, just wait for the next one and get a prime seat and enjoy the view.

Yes, mreynolds speaks the truth: the public bus ride is cheap, easy and gets where you are going in a reasonable amount of time. It can be less than confortable, may take a while, and the bus of course will not stop at scenic spots for views and photos. So, if you can manage and afford to take a small group tour (as in the RS-related Mondo tours) or can hire a guide/driver/vehicle for the day, your day will likely be more satisfying. I myself did take the all-day Mondo tour one day in May 2014, with stops in Positano, Amalfi and Ravello, plus a lunch stop and various short stops along the way. Then a couple days later, I went back by SITA bus to spend more time in Amalfi and Ravello. I did experience waiting in lengthy lines for the next bus, and then the next., and that was in the lovely and comparatively slow month of May.

You could also take the Coast to Coast bus service to Amalfi and then either catch their bus up to Ravello or the Sita service whichever is the most convenient. It is more expensive but they do not allow standing on the buses so they do not get crowded like the Sita buses and there are fewer stops. Tickets are bought from the staff on boarding so you are not commited to using their service for all legs of your journey.

http://www.sorrento.city-sightseeing.it/eng/percorsi.html