Whilst looking around the Fairy Tail tag, I was looking again at a question [here][1] asked by Shinobu, I finally decided to pop the question "How old is Natsu". I thought it would have been revealed further on in the series, but from the looks of it they haven't although the ages of Lucy, Erza and Gray have been revealed which is as follows

 1. Lucy- 17yrs
 2. Erza- 19yrs 
 3. Gray- 18yrs

Has an age ever been given in the mangas to how old Natsu is?

 

  [1]: https://anime.stackexchange.com/questions/7620/why-cant-natsu-and-gajeel-go-through-freeds-runes