Developing a usable vocal range of 2 octaves is a great goal. The typical vocal range is anywhere from 2 octaves to 3 octaves. An octave is eight steps in a major musical scale, including the semi-tones found between those 8 steps. If you can locate a C, for instance, on a piano keyboard, from that C, to the next C, to the next C is 2 octaves. Trained singers often can sing from 2.5 to 3 octaves, or more.
Untrained singers often believe they have a range of only a few notes, less than an octave. This is because they are attempting to sing in a way that doesn't allow the natural voice to flow freely, and/or they are trying to sing notes in the extreme low or high ranges that do not fall comfortably within their natural voice range. Establishing the low and high capabilities of your voice is essential to finding and developing a decent vocal range.