When I came back from Israel to make the conenction to my SJC flight at JFK I decided to time it although I had 6 hours to spare and my El Al Flight was delayed which was good in a way so I would not wait too long at JFk. I timed it just for the heck of it. I set my stopwatch and off I went. From the aircraft in Terminal 3 to customs took 5 minutes. I actually ran so that I would beat the rest of the flight. Getting through customs only took 5 minutes. Getting my bag another 15 minutes. Checking my bag to SJC 5 minutes and going from the bag recheck to my next gate 15 minutes. So roughly it took and hour. I found that by running to customs is a good way as it will actually wake you up and will cut down in the customs line.

In Israel from the plane to the public area took 40 minutes. Since I knew the old terminal I went into my own line as opposed to the longer group line. Also I did not want the leader to have my passport. It saved me loads of time and they did not ask many questions.

So yea I would allow 3 hours-5 hours from International-Domestic and 2-3 hours for Domestic-Internatonal since the plane could be delayed.