Help understanding fermentables and attenuation

[ahpsp]

I'm a very new brewer and I've read quite a bit. I'd like some help in understanding how to calculate fermentables in a wort, and the relation of yeast attentuation to fermentables.

I believe I understand the general principle between mashing low and getting a more fermentable wort. How does one use the mash temperature information to calculate how much sugar is available for conversion from, say, a pound of two-row? Then, once one knows that, when you're looking at attenuation percentages for yeast, is that the attentuation of those fermentable sugars? In other words, assuming corn sugar is 100% fermentable, will a yeast with 70% avg attenuation only convert 70% of that corn sugar to alcohol?

Thanks.

 

[helibrewer]

Fermentables have point-per-pound-per-gallon units. Extract is around 1.046 or 46 points per pound per gallon of wort. Base grains are around 1.035 or 35 points per pound per gallon. Using these units you can calculate your grain bill and know the potential for the wort. This is how the OG is derived.

How well the yeast actually ferment this wort results in your FG. The difference between the OG and FG gives you the Apparent Attenuation of the wort, i.e. how well the yeast did at converting the fermentables to alcohol and CO2.

So if you do the math and your grain bill produces an OG of say 1.050 and your yeast attenuates around 75%, your FG should be close to 1.012