Detail the ibu approximation formulae

[rocketman768]

What are the various ibu estimation formulae, and what is their exact representation for metric units? Also, what are the pros/cons or strengths/weaknesses of each?

Thanks.

 

[kladue]

I went with the Tinseth formula as it appears to work over the normal range of beer styles without resorting to a lookup table. There is the divide by variable "/(4.15)" in the boil time factor that is a convient way to tune the calulation to actual system utilization. It looks like the other formulas are simplified with tables and factors used above 1.050 gravity worts, but I have not tried any of them to pass judgement on their accuracy.

 

[rocketman768]

I found this article which explains 3 methods: tinseth, rager, and garetz. I emailed Tinseth asking him how to deal with the different forms hops may come in (whole, pellets,...) and how to deal with the fact that the the wort's gravity increases during the boil.

http://www.realbeer.com/hops/FAQ.html

 

[rocketman768]

Here is what Mr. Tinseth said...

I didn't do any research using pellets, so I can't really give you a number to use. I think that a 10% increase in util is commonly used, but my feeling is that the longer you boil hops, the less the original form matters. Still I have no data and so can only speculate.

For the boil gravity, I use an estimated average gravity over the course of the boil. Something like (start of boil grav + end of boil grav)/2