What's the minimum age needed while you are using an Interrail pass?

There is no minimum age for Interrail. There are many Interrail at the age of 16 and 17 years. It is important that a written consent of your parents (best in English) that you are allowed to travel alone, if you are still a minor. See the question about Interrail at the age of 17.

インターレイルパスを購入！