Many singers identify themselves based on their voice type, such as I'm a soprano, I'm a tenor, etc. Voice type is really based on two separate ingredients: range (which notes your vocal folds can produce) and timbre (the sound of your voice). But I bet that if you ask a singer what their range is, very few will actually have the answer. That's really odd if you think about it. Athletes know their height AND weight but singers can't tell you the highest or lowest note of their range.
What determines your range is the diameter of your vocal cords: the smaller the diameter (and hence) length, the higher your vocal range. An easy way to demonstrate this is to use coins as a visual example. Our smallest coin, the dime, illustrates the size of the vocal cords of the highest soprano; a penny works for the average female; for the average man, think nickel and for the lowest bass, a quarter..
Want to discover your range? It's pretty easy. First make the sound aw as in the word law or dog. Pucker your lips and allow your chin to go down at the same time. Now start on a lowish note and descend on a 5-note melody, 5-4-3-2-1 of the major scale to be exact. If you can hear your low note clearly, then adjust the pattern down a half-step (or semi-tone) and repeat the 5-4-3-2-1 pattern until your reach your lowest note. It doesn't have to be loud or even sound great. It just has to be there for it to count. When you find the note, write it down!
Since most singers have 3 and 1/3 octave ranges, even beginners, your high note can be estimated by knowing your lowest note. Even if you have actually less than 3 1/3 octaves, you'll probably discover that you can produce more notes than you had expected.
Here are some rough low notes and how they correspond to voice type:
F (below middle C) - high soprano (expect a high A on top)
D (below middle C) - regular soprano (I see this note ALL the time)
A/Bb - mezzo-soprano
F (2 below middle C) - alto (very rare voice type)
A (2 below middle C) - high tenor
E (2 below middle C) - tenor
C (2 below middle C) - 2nd tenor/high baritone
G (3 below middle C)- baritone
E ( 3 below middle C) - bass/baritone
C (3 below middle C) - bass
These are of course approximate. So how low can you go?