It seems to me that one of the only variables that you can measure about your beer is ABV. it's easy to measure gravity before and after fermentation. This tells you what your ABV is. I've read somewhere that IBUs can only be measured in a lab. I doubt that it's practical for a homebrewer to measure SRM either. Can carbonation be measured? I don't know how it could. Am I missing any other variables? Gravity, bitterness, color, and carbonation have to be the big ones. Keep in mind I'm referring to measuring a variable, not calculating it.