Tool
How far has my fermentation actually gone?
What proportion of the available sugar the ferment has taken, and why a dry cider reads over 100% on this scale while a perry reads low without having stalled.
Attenuation
Apparent attenuation
92.0%
How this is worked out
- Formula: apparent attenuation = (OG − FG) ÷ (OG − 1) × 100
- Substituted: (1.050 − 1.004) ÷ 0.050 × 100
- Result: 92.0%
What this assumes (3)
- This is *apparent* attenuation, measured by density. Ethanol is less dense than water, so a fully dry cider reads above 100% on this scale — which is a property of the measurement, not of the ferment.
- A perry will show lower attenuation than a cider fermented just as completely, because its sorbitol never ferments and continues to contribute density.
- Low attenuation with sugar remaining is not automatically a stall. Keeving, chilling and racking off the yeast are all deliberate ways of stopping short.
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