Find the lowest note of your vocal range. Sing a note that is in the middle of your range and play that note on the piano. This note will probably be close to the pitch at which you speak. Play descending chromatic notes on the piano and match them with your voice. Write down the lowest note that you can sing comfortably on the staff paper.
Find the highest note of your singing range. Sing the starting note in the middle of your range again. Play ascending piano notes and sing them until it is uncomfortable to sing any higher notes. Write down the highest comfortable note on the staff paper.
Look at your vocal range marked on the staff paper and match it to your voice type. Bass voices sing between the C two octaves below middle C to the E above middle C. Tenors sing notes that are between the B two octaves below middle C to the C one octave above middle C. Altos sing notes from the E below middle C to the E an octave and a third above it. Sopranos sing between middle C and the C two octaves above it.