I have a ignorant question. Is doing the calculation on paper (like above) close enough compared to taking the hydrometer OG reading? Also why not just do it all on paper (OG & FG) and get rid of the hydrometer?
YEAH! Thread Jacking... ....
Ok, well first most beer is brewed from grain, and you can't figure OG as the conversion from grain to wort can be affected and every brew can be different - although in practice, the typical AG brewer can tell you 'if I use Xlb of grain, I'll typically have an OG of Y with 5 gallons" But that is the 'typically' that screws that up.
Ok but what about Extract brewers? and OG?
Well did you put in 5G? 5.5? 4.5? because the og at 5G is about 10% higher than 5.5 and 10% lower than 4.5 (might be closer to 10.8% on both but not important).
Was that DME really a 45points per pound? or only 44points? and did you put in 3lb? or 2.9lb? (with about .1lb stuck to the bag?) etc etc. But a reading tells you what it is - assuming you mixed top off water well, or did a full boil.
On the FG, yeast has attenuation range of about 4% that is 73-77% is typical. Although some strains 4% around 80% and some are 4% aroudn 70%. With a varrience fo 4%, that 1.50 gravity beer can finish between 1.011 and 1.014 depending on a high attenuation or low for that strain.
And then don't get us started 'is it done yet?' Which is all about the FG being about what we should expect per strain. If you never do an FG, what if the gravity is stuck at 1.020, until you rack to bottling, and then the yeast wake up, and go fora nother .006? typical bottling sugar adds abotu .001 to the gravity. Imagine what happens when .006 is added? >BOOM<
Anyhow suffice it to say 'not measuring OG and FG' is like trying to tell if a person has a fever that is low and ignorable, medium and maybe some anti boitics, or high and needs a visit to the ER. ie just a guess. Can you make beer that way? sure they have and in some areas still do, but why no just take the measurement?