Will it pay off 7 days JP Pass

Hi,
We are going to spend 7 days in Japan, 3 days in Hokkaido, 4 days in Tokyo. Will JP pass pay off during this trip?
Or Should I buy the regional JP pass, take the flight(air passes) from Sapporo to Tokyo?
Thanks.

Where do you enter Japan? Where do you leave? Where in Hokkaido do you go? All these answers will be essential to give you a clear answer.

Generally speaking, the cheapest and fastest way to travel is by Skymark Airline. The airline serves Sapporo and Asahikawa.

Thank you promt reply. I am planning to arrive at Sapporo, leave Japan by Tokyo. My husband and I together with 3 years old girl. 3 days : Sapporo-Hakkiato-otaru, 4 days: Tokyo.

I'm not sure of the costs itself, but I think it will be easier to take a flight from Sapporo to Tokyo. The main reason is that to get to Tokyo from Sapporo by train, you either have to:
i) Take a sleeper train (which has some additional fees in addition to the JR pass)
or ii) stay a night somewhere between Sapporo and Tokyo and take day trains.

Flying will be more convenient and will most likely be cheaper. Don't get me wrong, the trains would probably make for a fantastic experience. However since you are only in Japan for a limited number of days, I'm sure you don't want to spend too much of your time travelling when you could be doing something else instead.

i) Take a sleeper train (which has some additional fees in addition to the JR pass)
or ii) stay a night somewhere between Sapporo and Tokyo and take day trains.

A third option would be to take daytime trains from Sapporo to Tokyo without overnighting anywhere along the way.

The one way fare from Sapporo to Tokyo by daytime trains is around 23,000 yen, which is less than the 28,400 yen for a 7-day Japan Rail Pass. Here are your options for travel between Sapporo and Tokyo:
http://www.japan-guide.com/e/e5306.html

i don't know where you are flying from or what is available in other countries, but in the US, if you are flying on JAL or ANA, you can purchase an airpass. 10,000 yeb for JAL and 13,000 for ANA (i think). there are some dates that are you can not use an airpass.

this may or may not be cheaper than a 7 day rail pass or JR east pass when you consider the extra fees and how much you plan to travel on a JR train in Hokkaido and Tokyo.

you must choose your travel dates and purchase your tickets before you leave for Japan.