For IBUs I would keep it simple starting out - BIABacus helps a lot - under section D there is a place to enter desired IBUs, just plug in the number you want, so for a Belgian Strong ale I would put in a number between 15 and 30. After you brew and taste test you can tweak the next brew, and the next, and the next...
IBU attempts to but a number to the bitterness but the reality is that attaching a number to the sensory aspects of our perception of hop bitterness is challenging, mystic, future science... etc.
The way I see it, IBU gives you a general idea of the bitterness expected - when I think of different recipes I think "ranges in bitterness" that I want. Calculating/measuring it is a challenge, there are three calculations that I know of Tinseth (BIABacus uses), Rager, and Garetz. They all provide a number from a calculation all likely different from a laboratory measurement.
Sticking to one type of calculation lets you develop an understanding of how your beer will come out, helps you maintain consistency (which I believe is the whole purpose of the IBU) - and you adjust from there based on if you want more or less bitterness. I think tinseth is the most commonly used.
I read somewhere Tinseth was a homebrewer (gets points there) and developed it while studying for his PhD in Chemistry. (useless information
)
I think what you will hear from others is - chill on the IBU calculations - figure out your system first, get some recipes under your belt, pay attention to your main ingredients, and you will brew better and better tasting beer. Consistent brewing practice is more important than which formula to use...
So, on the keep it simple (I am a follower of the KISS model), if you want a Belgian Strong - look up the judging specifications (which
I early gave you the Belgian Blonde specs
, a Belgian Golden Strong is OG (1.070-1.095) FG (1.005-1.016) and IBU 22-35 (sorry on that) - Ask yourself what numbers in those ranges you want and plug them into BIABacus. In this case and IBU of 30 works -plug it into BIABacus, brew, taste and tweak recipe, brew again - never ends - like the instructions on the shampoo - lather, rinse, repeat... brew, taste, repeat
Pete
(oh yeah - reminder - search the site, there have been some good discussions on this, form which I learned)