How old was Harry Potter when he told a wizard?

This question is a bit tricky! It depends on what you mean by "told a wizard."

Here are a few possibilities:

* When Harry first met a wizard: Harry was 11 years old when he met Hagrid, who told him he was a wizard.

* When Harry learned he was a wizard: This also happened when he was 11 years old, during the same visit from Hagrid.

* When Harry told someone he was a wizard: Harry probably told his friends Ron and Hermione he was a wizard soon after they met at Hogwarts.

Let me know if you had a specific situation in mind, and I can give you a more precise answer!