Beer ABV Calculator
Enter your original gravity (OG) and final gravity (FG) to calculate alcohol by volume and apparent attenuation. Updates as you type.
About the formulas
Standard: ABV = (OG − FG) × 131.25. Quick and accurate for most beers under ~1.080 OG.
Alternate: ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794). Better for high-gravity beers (imperial stouts, barleywines, big IPAs) where the standard formula tends to underestimate.
Both numbers are apparent ABV from hydrometer readings, not corrected for residual sugar. For competition or labeling, use a calibrated instrument and the alternate formula above ~8% ABV.
Beer ABV calculation FAQ
What is original gravity (OG)?
The density of your wort before fermentation, measured with a hydrometer or refractometer. It tells you how much fermentable sugar is in the wort — more sugar means more potential alcohol.
What is final gravity (FG)?
The density of your beer after fermentation. Yeast convert sugar to alcohol and CO₂, so FG is lower than OG. The difference between OG and FG is what the ABV calculation is based on.
What is apparent attenuation?
The percentage of fermentable sugars the yeast converted. A typical clean ale yeast attenuates 70–80%. Higher attenuation means a drier finish; lower means more residual sweetness.
Why are there two formulas?
The standard formula is a linear approximation that breaks down at higher gravities. Above roughly 1.080 OG, the alternate (Miller) formula gives a more accurate estimate because it accounts for the non-linear relationship between gravity drop and alcohol production.
Pouring this beer commercially?
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