I was trying to figure out my voice range, but I actually run against the stupid problem that I don't know if I sing a c3 or a c4. I was using an online piano to match my voice, but I simply don't know if I'm singing a c3 or a c4 to match the note I hear from the piano. (I am sure I'm singing a c, though.)
I've found a video of a guitarist explaining how to determine it, but I am being insecure about it. I probably have a range of something like c2-e4 or a few notes higher, but hey - it might be an octave up?