How do i know if my bass is tuned to C correctly?

i just tuned my low e string to C so it would sound better when playing SOAD seeing as how most of there songs are on only one or two strings.


its tuned to C but its really loose and buzzes off the frets so im not sure if its right

How do i know if my bass is tuned to C correctly?
If you're going to tune down that far, you'll need thicker strings, and possibly a neck tweak.