time to clear customs in rome

International arrivals are one time that I don't try to pre-purchase
a ticket – except in a few cases in which the discount ticket was so cheap that I didn't care if I lost it... it was a reasonable gamble. It's too hard to predict how many other flights will be arriving at the same time, and therefore how long airport formalities will require.

If you want to give it a try, I would suggest allowing 3 hours, maybe 4 hours if you're not familiar with the airport and the station. I hate the stress of sprinting through an airport or train station with luggage, particularly when jetlagged. If you're okay with that, you could probably shave a some time off my estimates.

Direct trains only run from Roma Fiumicino to Venezia S. Lucia stations twice daily at 11:08 and 15:08. As long as there is no significant flight delay, you should be able to make the 11:08 departure. But if you book the ticket ahead and miss the train, then it doesn't help you to get on any later departure; you'd just buy a new ticket. At other times of day, you take one of the frequent shuttle trains into Roma Termini and connect there to fast trains that run hourly. These are not likely to sell out.

Your biggest bottleneck will likely be going through passport control. After that it's getting your checked luggage if you have any.

If you have nothing to declare, customs is a walk-thru totally disinterested guys on the way out of the airside.

Turn right and walk the equivalent of about 2 blocks still inside the terminal, but on the public side, to find the way to the train station on the left. The station is actually across the street from the terminal. There is a booth immediately to the left inside the train station where you can buy tickets or get help in English if you already have them.

We were able to get tickets to Roma Termini, from there to Milano Centrale on a freccia fast train, and from there to the Milan airport all from the person in that booth and using my credit card. You should be able to do something similar for Venice if you need to do that.

Laura's take is the best bet to get to Venice direct(through Termini) to Venice. They just started this service a little while ago, and my Italian collegues catch the train in Bologne going to FCO and love the convenice. I believe the stops are Termini, Florence, Bologne, and Venice.

If you connect from another Schengen country and have nothing to declare exiting will be a cake walk. If you arrive from a non-Schengen country then passport control would be your potential delay, especially if you arrive at the same time as other non-Schengen flights.

You mean Passport Control? Customs occurs on the Return flight, and it could take place here or at an airport over there, depends on the Airline.
Anyway, Passport Control should Not take long. They look at you and your Passport. Lines could be long, but there are several agents on duty.

I do not understand the bit about the two direct trains per day. In daylight hours, there is at least one departure per hour from Roma Termini to Venice S.L, sometimes two.

"I do not understand the bit about the two direct trains per day. In daylight hours, there is at least one departure per hour from Roma Termini to Venice S.L, sometimes two. "

That's correct. What Laura was referring to was the new direct service from Roma Fiumicino station to Florence and Venice - that's the one that only runs twice a day. If those times don't work, then the "old standby" method is necessary - train from Fiumicino to Termini, then a separate train from Termini to Venice.

If flying directly from the US (no stop in Europe) then you will go through both immigrations and customs. With an 8 am arrival it most likely is a direct flight. Customs is always a walk through the "Nothing to Declare" door. Immigration is dice roll. Last May on a Saturday 8am arrival from New York it was two and half hours. Lots of other planes arriving at the same hour and two immigration officers on duty and they were in no hurry. It was a zoo. Other times we have sailed through in an hour. So don't plan your departure too tightly.