ABV Calculator
Alcohol by volume from original and final gravity - standard and high-gravity formulas.
Pre-fermentation, e.g. 1.050
Post-fermentation, e.g. 1.010
5.25% ABV
Standard formula5.25%
Alternate (high-gravity) formula5.34%
Alcohol by weight (ABW)4.16%
Apparent attenuation80%
How it works
Alcohol by volume is estimated from the drop in gravity during fermentation. The headline figure uses the standard formula; the alternate (Hall) formula is shown alongside for high-gravity beers.
ABV = (OG − FG) × 131.25
ABV(alt) = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794)
Sources: standard and alternate (Hall, Zymurgy Summer 1995) formulas as documented by Brewer's Friend. The most accurate high-gravity correction is the Balling/real-extract regression of Cutaia, Reid & Speers (2009).
Estimates for planning. Real ABV depends on attenuation, sugar adjuncts and measurement accuracy - confirm with calibrated readings.
Frequently asked questions
- How do you calculate ABV from OG and FG?
- The standard formula is
ABV = (OG − FG) × 131.25, where OG is original gravity and FG is final gravity. For stronger beers (OG above ~1.07) the alternate formula is more accurate. - Which formula should I use, standard or alternate?
- Use the standard formula for typical beers up to about 7–8% - it is accurate to roughly ±0.3%. Use the alternate (Hall) formula for high-gravity beers, where the simple formula increasingly overestimates.
- What is the difference between ABV and ABW?
- ABV is alcohol by volume; ABW is alcohol by weight. Because alcohol is less dense than water, ABW is about 79% of ABV. This calculator shows both.