What is the difference between apparent and real attenuation?

Apparent attenuation is calculated directly from hydrometer readings and overstates the true sugar consumption because alcohol is lighter than water, making the FG read lower. Real attenuation corrects for the presence of alcohol and gives the actual percentage of extract consumed.

What is a good attenuation percentage?

For most ales, apparent attenuation of 72-78% is typical. Lagers tend to be similar at 73-77%. Belgian and saison yeasts can attenuate as high as 85-95%. Very low attenuation (below 65%) may indicate a stuck fermentation.

Why does attenuation matter?

Attenuation determines the body, sweetness and alcohol content of your beer. Higher attenuation means a drier, thinner beer with more alcohol. Lower attenuation means more residual sweetness and body but less alcohol.

How can I increase attenuation?

Lower your mash temperature to 62-64°C to produce more fermentable sugars. Use a more attenuative yeast strain, pitch adequate yeast, ensure proper oxygenation, and ferment at the upper end of the yeast temperature range. Adding simple sugars also increases apparent attenuation.

What is the typical real attenuation compared to apparent?

Real attenuation is typically 12-16 percentage points lower than apparent attenuation. For example, if apparent attenuation is 75%, real attenuation is usually around 60-63%. This difference exists because alcohol makes the beer appear lighter than it truly is on a hydrometer.

BrewCalcs

Attenuation Calculator — Apparent & Real

Calculate both apparent and real attenuation of your fermentation.

Original Gravity (OG)

Final Gravity (FG)

How We Calculate This

Apparent Attenuation

AA = ((OG - FG) / (OG - 1)) x 100. This is the simple calculation from hydrometer readings but overstates actual sugar consumption because alcohol is lighter than water.

Real Attenuation

Real attenuation corrects for alcohol: RE = (0.1808 x OE) + (0.8192 x AE) where OE and AE are original and apparent extract in Plato. Then RA = (1 - RE/OE) x 100. Real attenuation is typically 12-16% lower than apparent attenuation.

Frequently Asked Questions

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Convert Brix refractometer readings to specific gravity.

Plato to SG Converter

Convert degrees Plato to specific gravity and back.

Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.