Attenuation

I keep hearing you guys (I mean people, sorry ladies) talking about the attenuation of the yeast. I believe I understand the concept but I was mainly wondering what the formula is to get the percentage. Also, where do I find what kind of attenuation my yeast can achive, do I just need to look up the brand of yeast that I am using?

I apologize if this was covered in "How to Brew," I'm still trying to make it all the way through it. Reading puts me to sleep...

Attenuation Formula:

FG = (1 - attenuation) * OG

Yes, you can look up the attenuation range for each yeast strain. 75% is pretty typical.

A wort with more fermentable adjuncts, such as corn sugar, table sugar, rice sugars, or honey, will yield an attenuation on the high side of the range.

A wort with a lot of unfermentable dextrines (by using a lot of crystal malts, or carapils, or malto-dextrin, or by mashing at higher temperatures) will yield a lower attentuation.

Thanks a lot! That's easy enough, if I could only remember to take an OG reading on my next brew...