calculate OG from Final

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eager_brewer

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I have a quick question. I pitched my yeast yeasterday and forgot to measue the OG first (I was in a big hurry). Is there anyway to find out what is was using the FG? Thanks!
 
Hmmm, I don't think so.

I mean, you could use the FG and then estimate the OG by the yeast strain's typical attenuation, but I think that would really be just a guess and not at all accurate. Some yeast strains average 65-72% for attenuation, for example, but you may occasionally get 78% with that same strain.

The easiest way I can think of to guess the OG would be to use the ingredients and a typical mash efficiency percentage.
 
There's a calculator in BeerSmith that will do it with a final hydro reading and a final refractometer reading. I have no idea how it works or if its accurate, but it might be worth looking into.
 
There's a calculator in BeerSmith that will do it with a final hydro reading and a final refractometer reading. I have no idea how it works or if its accurate, but it might be worth looking into.

It should be possible for this method to work. The gravity of pure alcohol solutions, at temperatures, is well known. The refractometer reading translates to sugar concentration, whose SG's are also known. A little arithmetic juggling and you should have it.
 
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