Work out alcohol by volume instantly with clear inputs, formula shown and shareable results.
The standard homebrew formula is ABV = (original gravity - final gravity) x 131.25, and apparent attenuation is the share of the original gravity points that fermented out. Attenuation tells you whether a stuck fermentation is the reason a beer is sweet and low in alcohol, which gravity readings alone do not reveal.
ABV
ABV % = (OG - FG) x 131.25
Attenuation
apparent attenuation % = (OG - FG) / (OG - 1) x 100
ABV % = (OG - FG) x 131.25. The standard homebrew formula is ABV = (original gravity - final gravity) x 131.25, and apparent attenuation is the share of the original gravity points that fermented out.
Attenuation tells you whether a stuck fermentation is the reason a beer is sweet and low in alcohol, which gravity readings alone do not reveal.
Enter original gravity, final gravity. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.