Well it all depends on what style of music you want to sing, for example if you where into singing death metal you would need a range that went very low so that you could do those deep roars ( screams ) but also very high so that you could add that intensity to your singing to match the music. This type of intensity is also very common now in pop music but the lows of death metal are not.

I would say as a general rule of thumb that two and a half octaves is fine but that three and above is where you really want to be! With two and a half octaves you will notice how much easier most songs are to sing, but the more demanding stuff will still be just out of your reach. Again it all depends upon what you what to sing, if you find that two and a half octaves is enough, then stick with that.

Registers

You can't talk about vocal range without referring to the different names given to the voice in different areas within that range. These areas are referred to as Registers not voices! But the term voice is used so much these days and every one knows what is meant by it that I will not try to confuse the issue, so I will also, on the rest of my site, refer to them as voices, i.e. Chest voice, mixed voice and head voice, but just remember that the correct term is register.

The chest voice covers the lower notes and can be felt resonating (vibrating) in your chest, it's correct name is the heavy mechanism. The vocal folds (vocal chords) are thickest here and the tone is heavy and dark.

The Head voice (also sometimes referred to as falsetto) is where your higher notes are sung, you will not feel your chest vibrating when you sing here. It's correct name is light mechanism. The vocal folds are thin here and the tone is light and bright.

The Mixed voice is exactly what it says; it is a mix (blend) of the heavy and light mechanism. It is normally the weakest of the three registers and needs a strong chest and head voice before it will work properly (not break!).

Whistle register is the highest register and gets it's name from it's timbre which sounds like whistling, if you would like to hear an example then click here