I'm trying to calculate HBU (manually). I've read a few things online that say:
AAU*amount of hops in ounces = HBU.
however, i came across this website http://www.picobrewery.com/askarchive/hoprate.html
that says HBU is equal to AAU*amount of hops in ounces*extraction efficiency (based on how much you boiled each hop for).
I've also tried a couple of online calculators and everything is giving me a differnent HBU number.
Any suggestions? Ideally I would like to do it manually.