A day is from midnight to midnight. As there are no overnight trains from London to Paris no journeys on this route will require more than 1 pass day.

You will have to give more details of whatever you have added to the pass if you want a better explanation.

Thanks for your quick reply. I clicked on a train leaving at eleven in the morning. Perhaps i should not have put london as a destination?  Or maybe it thinks its round trip?

The planner on the Eurail website doesn't work so do your own planning in e.g. Excel and calculate how many travel days you need.

Leaving everyday in the morning i would like to travel from london the end of september to paris, spend five days in paris, then to Frankfurt for four days, then to Munich for two nights, then Milan for two nights and finally Rome. I would fly from rome to london on october 16.  

When i plug in this itinerary eurail says i need a pass for six travel days. It should be five. Im doing something wrong. 

You are not doing anything wrong. The planner is crap and I have reported that to Eurail. 

Thanks!  Its crazy they wouldn’t have a workable program.  

I think you did just one thing wrong. If you put in London as your first destination, then the planner thinks your first journey is to London = 1 travel day. Then you head to Paris = 2nd travel day. But it seems that you just want to go from London to Paris as first trip. Of course this is just one travel day. But that's why it does count one day too much. May this be the problem? You may not choose your starting point as a destination to visit.

Sure, that must be the problem, thanks so much!

One of the problems with the planning tool is that it doesn't allow you to enter a starting point. That's why it always calculates at least one travel day too many.