Snow White-13/14
Cinderella-15 or 18
Aurora-16
Belle-19
Jasmine-i think 17
Pocahontas-20
Mulan-16
Tiana-19
Rapunzel-18

well, we know about snow white(14), aurora and ariel(16), tiana(19) and rapunzel(18).
i think cinderella is 18, belle is 19, jasmine is 16/17, pocahontas is 20 or older and mulan is 17/18

that would make jasmine pretty old, wouldn't it? cosidering the time era.

One's We're Sure About:
Snow White- 13 or 14
Aurora- Just turned 16
Ariel- 16
Jasmine- 15 going on 16 (it never says her age, but Tigressfan10689 says she read so in a DP book, and it sounds very familiar to me)
Tiana- 19
Rapunzel- Just turned 18 (she's 17 for a good half of the movie)

Estimated Ages (My Opinion):
Cinderella- 17 or 18
Belle- 19
Pochontas- 20 to 23
Mulan- 17

The estimated ages are based off of personality, actions, looks, and time period. For example, in Mulan's time and culture, girls were normally married off at between ages 15 and 17. Based off her actions and looks, she seems to be on the older end of that spectrum, making her 17.

actually the creators confirmed that tiana is 19

^^*edits list*