How to calculate yeast attenuation

[LuNchBoX1371]

Hey im new to brewing and i was reading john j palmer book and i am kinda stumped. In his book i didnt really understand the equation so i looked online and found one that was similar. So i put in the values that the article gave me and it worked but when i try and input my own statistics i come up with negative numbers. What is an equation for calculating apparant attenuation and how do i input it my self with my own numbers?

 

[Pie_Man]

Apparent attenuation is:
(OG - FG) / OG

Dropping the 1.x stuff makes the math easier. For instance 1.040 = 40, but 1.110 = 110.

If OG is 1.040 and FG is 1.010, (40-10)/40, 30/40 = 75% apparent attenuation.

 

[LuNchBoX1371]

Ok cool thanks but my OG IS 1.062 and my FG is 1.020. Does 10% attenuation sound right?

 

[LuNchBoX1371]

Nevermind i dropped the 1.x and it come out to 59%. But y is there such a big differance

 

[duboman]

62-20=42
42/61=69
or 69% apparent attenuation, which is a little light for a typical strain of yeast

 

[pedrovic]

Beersmith has an option called "Adjust FG Based on Mash Temp" (Options > Advanced) that, when disabled, solves the problem between FG and apparent attenuation.

 

[TaylorBrewed]

Get Designing Great Beers if you're looking to learn all the math behind brewing.