CEFR B2 "Vantage or upper intermediate":
* Can understand the main ideas of complex text on both concrete and abstract topics, including technical discussions in their field of specialization.
* Can interact with a degree of fluency and spontaneity that makes regular interaction with native speakers quite possible without strain for either party.
* Can produce clear, detailed text on a wide range of subjects and explain a viewpoint on a topical issue giving the advantages and disadvantages of various options.
IELTS 6.0 "Competent User":
Has generally effective command of the language despite some inaccuracies, inappropriacies and misunderstandings. Can use and understand fairly complex language, particularly in familiar situations.