Calculate alcohol content from gravity readings
Before fermentation (typical: 1.030 - 1.120)
After fermentation (typical: 1.005 - 1.020)
Alcohol by Volume
5.25%
ABV
ABW
4.17%
by weight
Attenuation
80%
apparent
Calories
112
per 12 oz
Residual Sugar
2.5°P
Plato
ABV vs ABW
ABV measures alcohol by volume, ABW by weight. ABW is ~20% lower since alcohol is lighter than water.
Attenuation
Higher attenuation means more sugar converted to alcohol. 75-80% is typical for most ale yeasts.
Residual Sugar
Remaining sugar affects body and sweetness. Lower FG = drier beer, higher FG = sweeter/fuller body.
ABV = (OG - FG) × 131.25
This is the standard homebrewing formula. For beers over 6% ABV, a more accurate formula may be: ABV = (76.08 × (OG - FG) / (1.775 - OG)) × (FG / 0.794)
Inputs
Result
ABV = (1.050 - 1.010) × 131.25 = 0.040 × 131.25 = 5.25%. ABW = 5.25 × 0.79336 = 4.17%. Attenuation = (0.040 / 0.050) × 100 = 80.0%. Calories = (1881.22 × 1.010 × 0.040) + (3.55 × 10) = 76.0 + 35.5 = ~155.
Inputs
Result
ABV = (1.065 - 1.012) × 131.25 = 0.053 × 131.25 = 6.96% (rounded to 6.95%). ABW = 6.95 × 0.79336 = 5.51%. Attenuation = (0.053 / 0.065) × 100 = 81.5%. Calories = (1881.22 × 1.012 × 0.053) + (3.55 × 12) = 100.9 + 42.6 = ~194.
ABV is calculated using the formula: ABV = (Original Gravity - Final Gravity) × 131.25. This measures how much sugar was converted to alcohol during fermentation.
Original gravity is the specific gravity of your wort before fermentation begins. It indicates the amount of fermentable sugars present. Typical range is 1.030-1.120.
Final gravity is the specific gravity after fermentation completes. Lower FG means more sugars were converted to alcohol. Typical range is 1.005-1.020.
Attenuation is the percentage of sugars converted to alcohol by yeast. Higher attenuation (75-85%) produces drier, more alcoholic beer. Lower attenuation leaves more residual sweetness.
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Last Updated: Feb 12, 2026
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