Child Link is 10. Adult Link is 17. .......I think
It is all about how you think about Zelda. If you think that "young Link" (age 8) is the "real link" the he is 8 but is you thing "Big Link" (age 14) is the "real Link" then he is 14.
Toon link: 16 link: 17-18 young link: 9-10
15 or 16 years old.
No ages are ever specified in Zelda so if one were to guess I'd say around eight or nine.