How old is little cosette supposed to be in Les Miserables?

Cosette is first introduced in Les Mis when she is only a year or two old. When Jean Valjean saves her from the Thenardiers, she is probably around seven or eight years old. Marius falls in love with Cosette when she is about fifteen and posesses a look that contains the innocence of her past and all the passion of her future. By the conclusion of the book, Cosette can be estimated to be between sixteen and seventeen years of age.