It’s hard to wrap your mind around the ages of actors playing teens on shows these days, let alone tracking their characters’ ages through the seasons. One minute they’re turning 17, the next they’re running their mother’s fashion line (yeah, we see you Blair (Leighton Meester).
Considering each season ends right before the summer, that would make them roughly 18 in season 2, 19 in season 3, 20 in season 4, 21 in season 5, and about 22 now, in season 6. We know it’s hard to be sure, considering ALL OF THEM DROPPED OUT OF COLLEGE and they’ve been drinking like NBD at bars since the first episode.
Since Jenny (Taylor Momsen) and Eric were freshman in season 1, they are likely about 20 now. As for Rufus (Matthew Settle), Lily (Kelly Rutherford), and the rest of the older generation, it’s hard to say. Rufus dates and slums like he’s in his 20s (musicians, guys), and Lily is married to the dead.