I like Math. I like Beer. This is some of the math you use while making beer.
is the volume of the carboy (or your fermentation container)
is the volume of the pot
is the measured original gravity (in platos - i.e. the 52 in 1.052)
IBU is a measurement of the parts-per-million of isoHumulone in your beer. IsoHumulone is the isomerized alpha acid Humulone. Isomerization occurs during the wort boil. Read here for a more thorough discussion.
is the time the hop addition spent boiling
is the weight, in ounces, of the hop addition
is the alpha value (a whole number percentage) of the hop addition
is the volume of the carboy (or your fermentation container) in gallons
is an empirically derived model for utilization, which is described here.
This wikipedia page lists IBU values for common styles of beer.