Beer ABV Calculator

Beer ABV: (OG − FG) × 131.25

ABV (Alcohol By Volume) is how much pure ethanol a drink holds, expressed as a percentage at 20 °C. Homebrewers usually start with the plain version, ABV ≈ (OG − FG) × 131.25. Here OG is the Original Gravity, the specific gravity of the wort before fermentation, and FG is the Final Gravity, measured after the yeast has turned the sugars into alcohol and CO2. So OG = 1.060 and FG = 1.012 gives you ABV ≈ (0.060 − 0.012) × 131.25 ≈ 6.3%. Once a beer climbs past 6-7% ABV the simple math drifts, and a tighter correction is ABV = (76.08·(OG−FG)/(1.775−OG)) · (FG/0.794), which accounts for the non-linear link between sugar attenuation and alcohol. As a feel for typical numbers: Lager 4-5%, Pilsner 4-5.5%, IPA 5-7%, Double IPA 7.5-10%, Imperial Stout 9-12%+.

Applications

Planning homebrew recipes and checking quality, running and labeling a craft brewery, making sake and wine (the gravity principles carry over), the Brazilian artisanal brewing scene, staying within ANVISA/MAPA labeling rules (Brazilian law wants ABV on the label, with ±0.5% tolerance), sorting out tax classification (alcohol excise tracks the ABV bracket), and teaching people about responsible drinking.

FAQ

What is specific gravity? It's the density of the wort or beer compared to water (1.000). Read 1.050 and the liquid is 5% denser than water, thanks to the dissolved sugars. You measure it with a hydrometer or a refractometer.

Why does the formula multiply by 131.25? It's an empirical constant that ties the drop in gravity to ethanol percentage by volume. It assumes brewer's yeast attenuating somewhere around 75-80%, and it holds up well for beers up to about 6% ABV.

What is apparent attenuation? It's the share of sugars the yeast ate through, found with (OG − FG)/(OG − 1) × 100. Ale yeasts usually land at 70-80%, lager strains at 75-85%, while champagne and saison yeasts can push past 90%.