Hop calculation/measurement

[spgriffin]

What hop measurement is better to use and why (Rager, BeerTools, etc)?

I notice in some recipe books, authors/ contributors do not state which they use which at first was frustrating when I would enter it into BeerTools and the IBUs where way off until I played with how they might be measring them.

[slothrob]

The "best" IBU formula is the one that gives the best approximation of the utilization you get from your system, as IBUs achieved from the same recipe vary wildly from brewer to brewer (as much as 25% or more).

However, it is popular for extract brewers to use Rager, as it takes into account the concentrated boil and final dilution with water. Alternately, Tinseth is preferred by many all grain brewers as it is intended for full volume boils and accounts for most of the variables that are considered important.

Many people seem to feel that Tinseth gives a good approximation of IBUs, and it is widely used, but it will probably be wrong if applied to a partial volume boil with dilution.

[jawbox]

Yeah Sloth has given yet more good advice. Although I've found myself go back to the rager formula even on full wort boils since it appears that most recipies in Zymurgy and the brewing network are utilizing the Rager formula.
I think Ive about recalibrated my tastebuds to it too.