Board Thread:General Discussion/@comment-38275329-20190926190625/@comment-4010415-20190927000108

73.Anon.52 wrote: Ruby was 15 at the start of the series, 16 in V5 was a fandom estimate based on seasons passing, but we got 17 from a CRWBY member at panels, We know the others are 2 years older than she is, but not their birthdays... if they are Nov-December babies, they should still be 19 even if she is 17, but 20 if they have earlier B-days. Gonna point out, 16 isn't just a fandom estimate, since Gray actually called her 16 years old during Volume 4's air time. We have a citation for it in her infobox. Gray tweeted a photo of Miles resting his head against a Volume 4 Ruby body pillow, commenting that Miles shouldn't get too comfortable because she's only 16.

Later, during Volume 6 airing, it was said in RWBY Rewind that Ruby has turned 17.