alcohol
s ci e n c e
And then, if the SG value for the beer has also been
be reported both % by weight (wt.) and by volume (vol.)
determined the alcohol by volume can be deduced with
to two decimal places. For reporting purposes brewers
a correction to account for the specific gravity of the beer:
in the US are allowed a tolerance of +/- 0.3% alcohol by volume (see American Society of Brewing Chemists,
ABV ( % by vol ) =
ABWt × SG beer SG ethyl alcohol at 20 0C / 20 0C
2017). Armed with the set of principles, equations and tables defined or referenced above - if the brewer can obtain either reasonably accurate Plato extract values or SG
Where: SG is the specific gravity, e.g., for the beer or pure
values for the original extract (gravity) of their wort and
ethanol respectively.
the terminal (apparent) extract gravity of the resulting beer – as well as real extract (measured or calculated),
This simplifies to:
ABWt × SG beer ABV = 0.7907
via use of hydrometers, refractometers or simple digital density meters, they can get quite close to true alcohol results for beers with low to reasonably high alcoholic strengths – typically 2.5-12% ABV and real extract values of around 2.5-8 degrees Plato (see caveats in Spedding, 2016). Furthermore, with the real extract value for the beer
in hand several other useful equations can be applied as
Variant equations are available but alcohol should
described below.
brewersjournal.info
September~October 2017
77