I've been using This picture from beersmith.com of a refractometer (Looks like the same refractometer as mine) scale to go back-and-forth between my brew notes (at the computer) when doing ABV calculations. I sometimes record the SG reading during the brew because I'll have the target OG of the recipe in mind and just not "thinking" in Brix.

Today, I noticed the scale at beersmith and the one in my refractometer (pic below) are not the same! Shouldn't both just be representative of the mathematical equations to convert Brix <> Wort SG @ 20C?

Other than a crummy QC process at the factory, is there another reason these two scales would be so wildly different (eg: compare at 16 Brix and then again at 29 Brix)?

My scale

  • Might be due to point #2 from here perhaps? homebrew.stackexchange.com/a/10916/18441 I have seen this mentioned elsewhere too, but I'm far from an expert. – thisextendsthat Aug 26 at 15:52
  • Aha.. that must be it: "...equation to convert from degrees Brix to specific gravity that was incorrectly published on byo.com. ". According to this calculator, I've got an accurate scale (brewersfriend.com/brix-converter) at least..as long as their calculator isn't based on the bad formula. If you want to post your comment as an answer I can give you the internet points for it ;) – HomeBrew Aug 26 at 17:34

Simple. The SG scale is wrong. Only use Brix. A refractometer is incapable of measuring SG. It's an approximation, and in this case especially, it's pretty far off.

Instead of using that SG scale, use a conversion tool like this, which is way more accurate when done properly, both for OG and FG:



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