Glossary
Apparent attenuation
Attenuation calculated from gravity readings without correcting for alcohol, which makes it read several points higher than the true figure.
Ethanol is less dense than water, so its presence pulls the final gravity reading down beyond what sugar removal alone would explain. The result is that the apparent figure overstates how much sugar actually went.
Real attenuation corrects for this and typically comes out around four-fifths of the apparent figure — a beer at 80% apparent attenuation is nearer 65% real. Almost every published attenuation figure, including yeast manufacturers’ specifications, is the apparent one, so comparing an apparent figure against a real one is a common and quiet error.
Commonly misunderstood
Quoted attenuation figures are almost always apparent, not real. Comparing a yeast supplier’s apparent figure against a laboratory real figure understates the yeast by roughly fifteen points.
Related
- Attenuation — The concept this is the standard expression of.
More vocabulary
ABV · ABW · Alcohol unit · Alkalinity · Alpha acid · Attenuation · Beta acid · Cohumulone · Degrees Lovibond · Degrees Plato
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
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Apparent attenuation is calculated without correcting for ethanol, which is less dense than water, so it reads several points higher than real attenuation — typically around 80% apparent for roughly 65% real.
Backed by a source
Sources: Brewing: Science and Practice — print; Yeast: The Practical Guide to Beer Fermentation — print