Calculate alcohol by volume and attenuation from specific gravity readings.
Fermentation converts sugar to alcohol, lowering density, so the gravity drop is proportional to alcohol produced. Attenuation shows how completely the yeast worked, with 70 to 80 per cent typical for beer. A stalled fermentation shows as low attenuation with a high final gravity, which this distinguishes from a deliberately sweet finish.
Beer/Wine ABV
ABV ≈ (original gravity − final gravity) × 131.25
This calculation is for brewing and winemaking reference. Alcohol content should be verified independently before any labelling claim, and home production is subject to local law.
ABV ≈ (original gravity − final gravity) × 131.25 Fermentation converts sugar to alcohol, lowering density, so the gravity drop is proportional to alcohol produced. Attenuation shows how completely the yeast worked, with 70 to 80 per cent typical for beer.
A stalled fermentation shows as low attenuation with a high final gravity, which this distinguishes from a deliberately sweet finish.
This calculator takes 3 inputs: Original gravity, Final gravity, Batch volume. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.