Here they are, (Note: these are just guesses, none of the charaters have said how old they are so it's really up to you.)
Candace-16
Perry-unknown
Isabella-9
Baljeet-9
Dr. Doofenshmirtz-40
Monogram-50
Carl-17
Jeremy-17
Stacey-16
Jenny-15
Fire site Girls-7-10
Linda-30
Lawrence-31
Pinky-unknown
Susie-5
Vanessa-16
Norm-proberly about 3 or 4
Grandmas and Grandpas-80
Irving-8
Albert-19
Django-9
Farmer and Wife-50
Love Handel-30
Well, I think that's it!
Hope it helped!
Phineas Flynn: 10
Ferb Fletcher: 11
Candace Flynn: 15
jeramy johnson:16jeramy
Isabella Garcia-Shapiro: 10
Buford Van Stomm: 11
Baljeet: 10
Django Brown: 10
Gretchen (fireside girl): 12
Holly (fireside girl): 11
Katie (fireside girl): 11
Milly (fireside girl): 11
Ginger (fireside girl): 10
Adyson Sweetwater (fireside girl): 12
Melissa (younger fireside girl): 5
Suzy Johnson: 5
Irving: 10
Vanessa Doofenshmirtz: 16
Stacy Hirano: 15
Jenny: 14
Mindy: 17
Wendy: 15
Linda Flynn-Fletcher: 35
Lawrence Fletcher: 38
Heinz Doofenshmirtz: 41
Charlene Doofenshmirtz: 39
The person who does the role of Phineas (Vincent Martella) is 17years old and the role of Ferb (Thomas Sangster) is 20years old.
Phineas- 10
Ferb- 11
Isabella- 10
Buford- 11
Baljeet- 10/11
Candace-15
Linda- 46
Lawrence- 49
Jeremy- 16
Perry- 5 to 7
Doofenshmirtz- 47
Irving- 10
Albert- 13
Maternal Grandparents- 70- 75
Paternal Grandparents- 73- 79
Ginger (Fireside Girl)- 10
Holly- 10
Katie- 11
Milly- 11
Gretchen- 12
Adyson- 12
This is unknown because in none of the series have any of the characters said how old they are.
ferb is eleven and Phineas is eight
This is unknown because none of the series have any of the characters said, thought or wrote down how old they are.
approximately 11.
15 in s1 and 16 in s2
This is unknown because in none of the series have any of the characters said how old they are.
ferb is eleven and Phineas is eight
This is unknown because none of the series have any of the characters said, thought or wrote down how old they are.
around 10 years old
79
She is 15
8
Phineas (Vincent Martella) is 17 and Ferb (Thomas Sangster) is 19. But in the show they are probally 10 or 11.
7 years old.
16
im pretty sure she is as old as phineas who it probably 9 or 10
probably about ten years old