Attenuation Calculator

Calculate apparent and real attenuation from your OG and FG readings. Helps assess yeast performance and fermentation completeness.

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Visualization

How It Works

Attenuation measures what percentage of sugars the yeast consumed during fermentation. Apparent attenuation (AA) is higher than real attenuation (RA) because alcohol is lighter than water, making the hydrometer read lower than the actual remaining sugar. Typical AA ranges: 65-75% for most ales, 75-85% for dry beers and saisons, 55-65% for sweet stouts and barleywines. If your attenuation is much lower than the yeast strain specification, possible causes include: mashing too high (creating unfermentable sugars), under-pitching yeast, insufficient aeration, or fermentation temperature too low. If attenuation is too high, possible contamination with wild yeast (Brettanomyces) that eats complex sugars.