User blog comment:PlantyThePottedPlant/Random Topic Blogging III: Blog Harder/@comment-3006892-20130512072002/@comment-4353345-20130514143055

Phineas: I want to say 12, however that seems a bit too young, but 13 seems a bit too old... let's just go with 13.

Ferb: I do agree that Ferb is probably older than Phineas, so probably 13 1/2

Candace: 15

Linda: 45, since she once dated Doofenshmirtz

Lawrence: 43

Stacy: 15

Isabella: 13 (I actually think Isabella might be just a few months older than Phineas)

Buford: 13

Baljeet: 13

Irving: 12, maybe 11

Doofenshmirtz: 47 (in one episode it actually said this was his age, but I can't remember which one. I do know it aired in 2012 and it featured his brother...)

Perry: 5, because they've had him for five years, as seen in the movie, but he looked very young and I suspect that, like training to become a Jedi, his secret agent training would have had to begin when he was no more than a year old. In platypus years, he's probably 21 or so

Jeremy: 16, since Candace said he's a year older than her

Suzie: 7

Vanessa: 16

If they were to actually advance ages, just add 5 to the ages listed above to get their current age.