Doug Murphy wrote:

Extra question for you all #2- Just exactly how old is everyone in Ranma?

Sixteen.  Time is suspended in the Ranmaverse.  Nine years are compressed
into one.

For real? Well, that will have to change when I do my fic. we will say that
1996 in Ranma makes everyone 16 and then they can age and develop from
there...

This is the way it is in most fics.  

--HAYES