Alcohol by Volume (ABV) Calculator

ABV Formula (Standard):

ABV = (OG - FG) × 131.25

ABV Formula (More Accurate):

ABV = (76.08 × (OG - FG) / (1.775 - OG)) × (FG / 0.794)

Where:

• OG = Original Gravity, the density of your wort or must before fermentation begins. You measure it with a hydrometer or refractometer on brew day.
• FG = Final Gravity, the density after fermentation is complete. When the reading holds steady for two or three days running, fermentation has finished.

The standard formula is what brewing software and style guidelines quote, and it works well for most homebrews. The advanced formula accounts for the changing density of alcohol in solution and pulls ahead on high-gravity brews. This calculator shows the standard figure as its answer below 10% and switches to the advanced one above that, where the 131.25 constant genuinely stops holding. Both are always printed, so you can see the gap for yourself.

Gravity Reference:

• Water = 1.000
• Typical beer OG: 1.035 - 1.090
• Typical wine OG: 1.070 - 1.120
• Typical mead OG: 1.080 - 1.130

Practical Example: If you brew a beer with OG = 1.055 and FG = 1.012: Standard: (1.055 - 1.012) x 131.25 = 5.64% ABV, which is the figure this page reports. The advanced formula gives 5.79% ABV for the same readings, a gap of 0.15% that is smaller than the error in reading a hydrometer. Attenuation works out at 78.2%, and the beer comes to about 183 kcal per 12 oz.

Common ABV Ranges:

Apparent Attenuation: This tells you what percentage of sugars the yeast consumed. Attenuation = (OG - FG) / (OG - 1.000) × 100% Most healthy fermentations achieve 70-80% apparent attenuation.

Common Mistakes:

• Forgetting to temperature-correct your hydrometer reading (most are calibrated to 60F / 15.6C)
• Taking the FG reading before fermentation is truly complete
• Confusing Brix or Plato readings with specific gravity. They are different scales, and 12 °Plato is 1.048, not 1.012.

About the calorie figure. It uses the Balling method: alcohol by weight, plus the real extract still left in the beer, weighted by the finished gravity. Roughly two thirds of the calories in an ordinary beer come from the alcohol rather than the residual sugar, which catches people out. A bone-dry 8% saison carries more calories than a sweeter 5% bitter, not fewer.