Board Thread:Theories and Speculation/@comment-2143336-20171001221219/@comment-32569165-20171002043634

Officially he got from Gennin to Hokage directly. Even in the Last which is supposedly 2 years after the war(and that's how much time Naruto needed to become Jonnin) he still had no Chunnin/Jonnin outfit, so he apparently didn't have either of those "ranks".