Number to percent

I have a spread sheet that calculates responses to questions, for example "yes" = 2, 'maybe = 1, and "no" = 0. The highest score for the 6 responses is 12. I need a formula that will say if the sum box = 12, then the rank is 100%, if the sum box = 11, the rank is 92%, etc. If any of the response are changed at a later time, so for example the sum used to be 10, but is now 12, the formula would re-calculate accordingly.