ABV (Alcohol By Volume) Calculator
Calculate the alcohol content of homebrew beer, wine, or cider from original and final gravity readings using both the simple and accurate formulas.
Results
What is it?
Alcohol By Volume (ABV) measures what percentage of a beverage's total volume is ethanol. In homebrewing, yeast consumes sugars and produces alcohol, lowering the liquid's specific gravity. By measuring gravity before (OG) and after (FG) fermentation and comparing the drop, you can calculate ABV. The simple formula (OG-FG) x 131.25 is accurate up to about 6% ABV; the more complex formula handles high-gravity beers and wines better.
How to use
Measure original gravity before adding yeast using a hydrometer or refractometer. After fermentation is complete and stable (same reading 2-3 days in a row), measure final gravity. Enter both readings — OG typically 1.040-1.100, FG typically 1.005-1.020.
Example scenario
OG = 1.060, FG = 1.010: Simple ABV = 6.56%, Accurate ABV = 6.63%, Apparent Attenuation = 83.3%. This is a typical American Pale Ale profile — moderate strength with good yeast health.
Pro tip
Apparent attenuation of 75-85% indicates healthy fermentation for most ale yeasts. If attenuation is below 70%, fermentation may have stalled — check temperature, pitch rate, and yeast health. Refractometers need a wort-correction factor after fermentation because alcohol changes the refractive index; use the Brix-to-FG calculator for accurate post-fermentation readings.