Alcohol by Volume from Gravity

The brewer's end-of-fermentation number. Specific gravity is density vs water (1.000); sugars push the ORIGINAL gravity above 1.000, and as yeast makes alcohol the gravity falls to the FINAL gravity. ABV% = (OG - FG) x 131.25: a beer 1.055 -> 1.012 drops 0.043 = ~5.6% ABV. Apparent attenuation = (OG - FG)/(OG - 1) = 0.043/0.055 = 78% (how much extract fermented). A 1.065 -> 1.010 wort is ~7.2% ABV, 85% attenuated. The 131.25 factor is an approximation that drifts high on strong brews (a more elaborate formula tracks better). A working estimate; a temperature-corrected hydrometer/refractometer and, for a sold product, the TTB/lab method govern the label.

abv_pct = (original_gravity - final_gravity) x 131.25; apparent_attenuation_pct = 100 x (original_gravity - final_gravity) / (original_gravity - 1).

Alcohol by volume from gravity (standard homebrew/brewing formula; Papazian, The Complete Joy of Homebrewing; ASBC context), by name; a temperature-corrected hydrometer or refractometer and, for a sold product, the TTB / laboratory method govern the label value.

The gravity-to-ABV relation is public brewing practice; the original and final specific gravities are the brewer's hydrometer readings.

Estimate. AHJ and licensed professional govern.

Field names used by the API: original_gravity, final_gravity, abv_pct, apparent_attenuation_pct

• Gravity-to-ABV ABV% = (OG - FG) x 131.25; apparent attenuation = (OG - FG)/(OG - 1); OG/FG are density vs water (1.000)standard homebrew formula (Papazian)
• Approximation limits 131.25 drifts high on strong brews (76.08 x (OG-FG)/(1.775-OG) x FG/0.794 tracks better); a temp-corrected hydrometer and the TTB/lab method govern a sold labelbrewing practice / TTB