On this page,
http://www.brewersfriend.com/brix-converter/
The formula used for brix to sg is listed as
Brix -> SG Equation:
SG = (Brix / (258.6-((Brix / 258.2)*227.1))) + 1
(Source: Brew Your Own Magazine)
But if you follow the link, that equation is for Plato (not brix). While plato, balling and brix are sometimes used interchangeably, they are in fact different, if I understand correctly. Plato and Brix begin to vary after ~1.060 and this is reflected in the conversions. BYO has a second article on refractometers where the formula for Brix -> SG is given as
SG = 1.000019 + [0.003865613(Brix) + 0.00001296425(Brix) + 0.00000005701128(Brix)]
This will give you about 1.116 for 30 brix, as where the formula used for the converter yields 1.1292. For 20 brix, 1.078 vs 1.0830. The values are closer as brix gets lower, so probably not a huge deal, but it does appear (at least according to the two articles) to be the formula for Plato->SG, not Brix->SG.
I kind of prefer the simple conversion, since it sits in between plato and brix and is simple enough to reverse
SG=1+(0.004*Brix)
Brix=250*SG-250
http://www.brewersfriend.com/brix-converter/
The formula used for brix to sg is listed as
Brix -> SG Equation:
SG = (Brix / (258.6-((Brix / 258.2)*227.1))) + 1
(Source: Brew Your Own Magazine)
But if you follow the link, that equation is for Plato (not brix). While plato, balling and brix are sometimes used interchangeably, they are in fact different, if I understand correctly. Plato and Brix begin to vary after ~1.060 and this is reflected in the conversions. BYO has a second article on refractometers where the formula for Brix -> SG is given as
SG = 1.000019 + [0.003865613(Brix) + 0.00001296425(Brix) + 0.00000005701128(Brix)]
This will give you about 1.116 for 30 brix, as where the formula used for the converter yields 1.1292. For 20 brix, 1.078 vs 1.0830. The values are closer as brix gets lower, so probably not a huge deal, but it does appear (at least according to the two articles) to be the formula for Plato->SG, not Brix->SG.
I kind of prefer the simple conversion, since it sits in between plato and brix and is simple enough to reverse
SG=1+(0.004*Brix)
Brix=250*SG-250
