Alcohol By Volume (ABV) Calculator

Food

The Alcohol By Volume (ABV) Calculator estimates the alcohol content of beer, wine or cider from the original gravity (before fermentation) and final gravity (after fermentation). ABV = (OG − FG) × 131.25.

Formula

ABV % = (OG − FG) × 131.25
  • Original gravity (OG) is the density of the unfermented liquid (wort or must) relative to water; final gravity (FG) is its density after fermentation.
  • As yeast converts sugar to alcohol, density drops, so the difference between OG and FG indicates how much alcohol was produced.
  • The common estimate is ABV % = (OG − FG) × 131.25.
  • This is an approximation; very strong brews may use a more refined formula, but 131.25 works well for typical beers and wines.

Example Calculation

Inputs
  • Original Gravity (OG): 1.05
  • Final Gravity (FG): 1.01

With an original gravity of 1.050 and a final gravity of 1.010: ABV = (1.050 − 1.010) × 131.25 = 5.25% ABV, a typical pale ale strength.

Frequently asked questions

What is alcohol by volume?
ABV is the percentage of a drink's total volume that is pure alcohol — for example, 5% ABV means 5 mL of alcohol per 100 mL of beverage.
How do I measure gravity?
Use a hydrometer or refractometer to read the density of the liquid before and after fermentation.
Why multiply by 131.25?
It is an empirical constant that converts the drop in gravity during fermentation into an alcohol percentage.
Is this formula exact?
It is a good approximation for typical beers and wines. Higher-alcohol brews may use a slightly more complex formula for better accuracy.
What gravity values are normal?
Beers often start around 1.040–1.060 OG and finish near 1.008–1.015 FG, depending on the style.