ABV Calculator

Calculate alcohol by volume for homebrewing.

Alcohol By Volume:

The Alchemy of Brewing: Measuring Alcohol by Volume (ABV)

For homebrewers, the most anticipated momentâ€”aside from the first sipâ€”is taking that final gravity reading. Did the yeast do its job? Is this a sessionable ale or a heavy hitting barleywine? Our ABV Calculator takes the guesswork out of brewing, converting your hydrometer readings into precise alcohol percentages using industry-standard formulas.

How Fermentation Works

To understand ABV, you must understand the magic of yeast.
Sugar + Yeast = Alcohol + CO2
When you make "wort" (unfermented beer), it is basically sugar water. Water is dense, but sugar water is even denser.
As yeast consumes the sugar, it produces ethanol (alcohol) and carbon dioxide gas. Alcohol is lighter than water.
Therefore, the density of your liquid drops over time. By measuring how much the density dropped, we can calculate exactly how much sugar was converted into alcohol.

Measuring Gravity: OG vs. FG

To use this calculator, you need a Hydrometer.

1. Original Gravity (OG):
This is the density of your wort before you pitch the yeast. It represents the potential fuel available.
Typical Range: 1.040 (Light Beer) to 1.100 (Imperial Stout).

2. Final Gravity (FG):
This is the density after fermentation is complete. Most of the sugar is gone, replaced by lighter alcohol.
Typical Range: 1.005 (Dry) to 1.020 (Sweet).

The Formulas

Standard Formula:
This works perfectly for most beers and wines under 10% ABV.
ABV = (OG - FG) Ã— 131.25

Example:
OG = 1.050, FG = 1.010
(1.050 - 1.010) = 0.040
0.040 Ã— 131.25 = 5.25% ABV.

Alternate Formula (High Gravity):
For high alcohol brews (over 10%), the relationship between density and alcohol content changes slightly because alcohol itself changes the fluid dynamics.
Formula: ABV = (76.08 * (OG - FG) / (1.775 - OG)) * (FG / 0.794).
Most homebrewers stick to the standard formula for simplicity, and our calculator provides that standard result.

What is Attenuation?

You will also see a result for "Apparent Attenuation." This tells you what percentage of available sugars the yeast consumed.
Formula: (OG - FG) / (OG - 1)
65-70%: Low attenuation (Malty, sweet beer like Scotch Ale).
75-80%: High attenuation (Dry, crisp beer like Saison or West Coast IPA).
If your attenuation is stopped at 50%, you might have a "stuck fermentation" (too cold or unhappy yeast).

Temperature Correction

Hydrometers are calibrated to read correctly at a specific temperature (usually 60Â°F or 20Â°C). If you measure boiling hot wort, the liquid expands and becomes less dense, giving you a falsely low reading. Always cool your sample to room temperature before measuring, or use a temperature correction tool.