Yeast Attenuation Calculatorv1.0.0

Determine how effectively yeast consumed sugars during fermentation by entering gravity readings from a hydrometer or refractometer. The calculator produces apparent attenuation, real attenuation, and alcohol by volume using both simple and advanced formulas.

• Enter your Original Gravity (OG) reading taken before fermentation begins. This value is typically between 1.020 and 1.130 for most beer styles. Accept decimal values such as 1.050 or fractions such as 1050/1000.
• Enter your Final Gravity (FG) reading taken after fermentation is complete. This value must be lower than the original gravity. Typical final gravity readings range from 1.000 to 1.030.
• Press the Calculate button or wait for automatic calculation after a brief delay. Results appear instantly below the input fields.
• Review the Apparent Attenuation percentage to see the gravity-based estimate that yeast manufacturers commonly reference. Compare it against the expected range listed on your yeast packet to evaluate performance.
• Review the Real Attenuation percentage for a more accurate measure that accounts for the presence of alcohol in the finished beer. Real attenuation is always lower than apparent attenuation.
• Compare the Simple ABV and Most Accurate ABV values. The most accurate formula (based on Hall Equation 16) accounts for alcohol density and provides better results for higher-gravity beers.
• Open Settings and enable Show step-by-step formulas to view the full derivation of each result, including the Plato conversion, attenuation formulas, and ABV equations with your substituted values.
• Press the Reset button to restore default gravity values and clear all saved state.

The apparent attenuation formula is AA = (OG - FG) / (OG - 1) x 100. Real attenuation uses the Plato scale: convert both gravities to degrees Plato, compute real extract as RE = 0.1808 x OGp + 0.8192 x FGp, then RA = (OGp - RE) / OGp x 100. The simple ABV formula is (OG - FG) x 131.25. The most accurate ABV uses Hall Equation 16: ABV = (76.08 x (OGp - FGp) / (1.775 - OGp)) x (FG / 0.794).

Evaluate yeast performance across a wide range of brewing scenarios. Track fermentation health, compare yeast strains, and troubleshoot stuck fermentations with precise attenuation measurements.

• Homebrewing: Measure how completely a yeast strain fermented a batch of pale ale with an OG of 1.055 and FG of 1.012 to verify the yeast performed within its expected 73 to 77 percent apparent attenuation range.
• Yeast Strain Comparison: Pitch two different yeast strains into identical wort samples and compare their apparent and real attenuation percentages to select the best strain for a recipe.
• Stuck Fermentation Diagnosis: Enter current gravity readings to determine whether fermentation stalled prematurely. An apparent attenuation well below the yeast strain's expected range indicates a potential problem with yeast health, temperature, or nutrient availability.
• Recipe Development: Predict the dryness and alcohol content of a new recipe by entering target OG and estimated FG based on the chosen yeast strain's published attenuation range.
• High-Gravity Brewing: Compare simple and most accurate ABV calculations for barleywines or imperial stouts where the OG exceeds 1.080. The difference between the two formulas becomes significant at higher alcohol levels.
• Quality Control: Track attenuation batch over batch for commercial or advanced homebrew operations. Consistent attenuation numbers indicate healthy yeast management and repeatable processes.
• Education: Learn the difference between apparent and real attenuation by toggling the step-by-step formula display and studying how alcohol density affects the hydrometer reading.