After the original Naruto storyline, there was a time skip of about two years during which Naruto went to train with Jiraya. Before he left, the bulk of the characters — including the Konoha 11 — were 12-13 years old. Once Shippuden began, however, they had all turned about 15. The sequel series took place over two years, but most of it happened while Naruto was around 16 years old.
Source:https://www.cbr.com/naruto-shippuden-characters-age/