If you are planning on using the 'Bullet' Trains a lot during your visit to Japan then you are sure to make some big savings. The map below shows a typical 14 day itinerary and gives an idea of the money to be saved by purchasing a 14 day Japan Rail Pass.
For 7 day rail passes, if you plan on making a return trip from Tokyo to Kyoto + one other journey, then the rail pass offers good value for money.

The above savings are based on an exchange rate of £1 = 125 JPY.