How do i know when my voice change?

im 15 and im a tenor but how do i know if my voice change to baritone?How do i know when my voice change?
Be aware of the notes you sing on pitch and watch for or listen for the notes that you start having problems reaching clearly or loud enough. Maybe use a piano or guitar and find out exactly what your current range is. Then pay attention to how and in what way that range changes over the years.

The good news is that I'm almost fifty years old and have been performing since I was 14. My range at 14 was substantially less than it is now. Today I can sing almost a full octave higher and lower than I could at 14. I believe that this speaks to the fact that vocal chords, just like any other muscle in your body, require practice, exorcise and frequent correct use.

With other words, don't scream until it hurts, don't smoke, sing with a belly full of air and treat your voice as a very expensive musical instrument.