Calculation of Attenuation and Alcohol Content
To calculate the attenuation please fill in the original and final gravity of your beer measured by a hydrometer (if you use a refractometer, the values mus be converted or better used in the refractometer correction page).
When you measure the final gravity of your beer using a hydrometer, the value is tampered by the alcohol. So this is only an apparent gravity. However, if you know the original gravity you can calculate the real gravity.
The alcohol be weight can be calculated from the difference of original and final gravity. The alcohol by volume is calculated with the help of the density.
The attenuation descibes the portion of the original gravity that can be fermented by the yeast. The apparent attenuation is calculated with the apparent gravity; the real attenuation with the real final gravity.
The energy content is builded from the alcohol’s energy and the residual extract, in which the alcohol outweighs by far.
- Hubert Hanghofer: Bier brauen nach eigenem Geschmack, S. 125