Ever wondered how many octaves your guitar has? Well the quick answer is that most guitars have just under 4 octaves! But each guitar is made differently so in order to find out how many octaves your own, personal guitar has, you have to do some counting!
Assuming you have a 6 string guitar and are tuned in standard tuning (EADGBE), the open Low E string to the second fret on your D string is one octave.
Then from there to the open High E string is 2 octaves.
From there to the 12th fret of the High E string is 3 octaves.
And this is where it gets different for different guitars. If you have 24 frets, you have exactly 4 octaves. My electric guitar has 22 frets, so I have just under 4 octaves.
A lot of acoustic guitars have even less frets! Also if you tune down to drop D, you technically increase your range by a whole step.
Hope this clears up any confusion about octaves on a guitar!