How many octaves is G0-B5?

G0 to B5 spans a total of 5 octaves. Specifically, G0 to G1 is one octave, and each subsequent G to G is another octave, leading up to G5. Then, from G5 to B5 adds two additional notes within that octave, which does not count as a full octave. Thus, the complete range from G0 to B5 is 5 octaves.