There are several different formulas and theories about what the best hop utilization calculations there are. So there's no way to get a "precise" IBU, but this will get you in the right ball park:
If you rush, you may still be able to get in on White Lab's annual QC day. For $139 you get tests of diacetyl and IBU’s, as well as alcohol, calories, color, real and apparent attenuation, microbiological contaminants, and chill haze.
There are several different formulas and theories about what the best hop utilization calculations there are. So there's no way to get a "precise" IBU, but this will get you in the right ball park:
Right. The key is to pick a formula and stick with it. Know what a certain level of IBUs tastes like with one formula and adjust your recipe accordingly. 30 IBUs with the Rager formula is different than the Tinseth formula, so you need to be consistent. In a way, it's almost arbitrary what formula you use. A 60 IBU commercial beer, brewed in a homebrew setting with identical recipes, is guaranteed to have a different IBU measurement.