simple fermentation question

[UltraHighABV]

How do I measure reaction completion?

For instance, I start fermenting with an OG of 1.096; how do I know what Im expecting it to finish at? How will I know when its x% converted to alcohol when I dont know what the final number is? What is the final number, and what does it depend on?

Thanks, I know this question will come across as very trivial, but I have no clue

 

[flars]

You can look up the estimated attenuation for the yeast to give you an idea what the final gravity might be, but there are many variables involved in getting to final gravity. The only way to know when your fermentation is complete is by taking specific gravity readings with a hydrometer. When the specific gravity stabilizes the fermentation is complete.
After about twelve days, from the start of fermentation, take your first specific gravity reading. Take a comparison reading three days later, if they are the same final gravity has been reached. If the FG seems to high there could be a problem with the fermentation, or the yeast used could be one that takes much longer to finish the last few points than another yeast.
You may want to leave your beer in the fermentor longer, depending on the type of beer brewed, for flavors to build and the beer to clear.

 

[hottpeper13]

If you use a program for your recipes it will tell you,but I don't use those so I take the yeast thru different worts made at varying mash temps,keep good notes and go from there. This is a long process,but very tasty.