Hi there - are you planning on travelling to Sapporo to Tokyo by plane or train?
To make a 14 day japan rail pass worthwhile, you should spend more than ¥45,100 on individual rail tickets in Japan.
Assuming you'll travel down to Tokyo by train, here are your base ticket costs:
- Sapporo(jr) > Furano: ¥6030, (160mins, 191km)
- Furano > Sapporo(jr): ¥6030, (160mins, 191km)
- Sapporo(jr) > Tokyo: ¥22970, (551mins, 1196km)
- Tokyo > Osaka: ¥13550, (194mins, 556km)
- Osaka > Kyoto: ¥540, (29mins, 42km)
- Kyoto > Osaka: ¥540, (28mins, 42km)
- Osaka > Tokyo: ¥13550, (194mins, 556km)
TOTAL: ¥63410 for 7 legs
As you can see from the costs, a 14 day pass will be well worth it if you travel down to Tokyo from Sapporo. If not, then it's marginal which one will offer the most value as the plain ticket cost drops to ¥40,440.
Personally, I recommend buying the rail pass here simply for the convenience factor - it will let you branch off on any day trips you like and is only ¥4660 more expensive. In fact, should you even do 1 decent day trip in addition to your itinerary you will be making good savings over single tickets. Interesting day trips you can add on from Osaka are to Hiroshima (¥19,500 return) and although the castle is shrouded for renovation, the exhibits around Himeji are still well worth a visit (¥6880 return from Osaka).
Hope this helps!