ABV Calculator

Enter the original gravity you measured before fermentation and the final gravity after it finished, and this returns the alcohol by volume along with the gravity drop and the apparent attenuation. Two published formulas are shown: the simple rule of thumb, ABV equals the gravity drop times 131.25, and the alternate formula from Michael Hall's 1995 Zymurgy article, which tracks strong beers better. Under about seven percent the two agree closely, and above it the simple one usually reads low. A second mode works backwards to the original gravity you need for a target strength. Every figure here is an estimate from hydrometer readings, not a measurement of the alcohol itself.