There is a lot of flexibility in the Hokkaido Rail Pass: It comes as a 3-days / 5-days / 7-days pass (for consecutive day travels), or flexible 4-day pass which can be used on any 4 days over a period of 10 days.
The official price of the passes are currently as follows:
However, you can get the passes for slightly cheaper from Klook.
To determine if the Hokkaido Rail Pass is worth the money for your travels, you need to search for your train routes and pricing using hyperdia and compare the total of individual train fares to the price of the Hokkaido Rail Pass above.
The Hokkaido Rail Pass need not be bought from your home country, you can buy it after arriving in Hokkaido. However if you want to save travelling time (coz who wants to spend precious vacation time queueing up at ticketing counters and trying to play charade with staff who may not be proficient in English right?), we recommend you secure your passes online before your trip. Our preferred travel agent for getting all sorts of rail passes in Japan is Klook. It is a little cheaper to buy from them than to buy it after you arrive in Japan.
Note that if you buy your rail passes outside of Japan, what you will receive is an exchange order and not the actual pass. You will still have to exchange that for the actual pass when you arrive in Japan. This applies to all kind of rail passes and all authorised travel agents outside of Japan.
I have found the 4-day flexible pass great for side trips from Sapporo. This was how I utilized my 4-day flexible pass:
For a weekend in Hakodate:
Day 1: Sapporo – Onuma Koen – Hakodate
Day 2: Hakodate – Sapporo
For day trip to Asahikawa
Day 3: Sapporo – Asahikawa – Sapporo
For day trip on the Okhotsk no Kaze / Ryuhyo Norokko Trains
Day 4: Sapporo – Abashiri – Shiretoko – Sapporo