Real Attenuation

The attenuation of beer after alcohol and carbon dioxide is removed. In the brewing industry only the apparent attenuation is used to measure the progress of fermentation. Formula A = (B-b)/B x 100 where A equals real attenuation and B equals original gravity in degrees B or degrees P and b equals specific gravity of beer devoid of alcohol and carbon dioxide. Real attenuation (extract) may also be calculated from the apparent attenuation RA = AA + (alcohol by weight x 0.46) Thus, a beer with an apparent extract of 2.6, and 3.7 percent alcohol would have a real extract RE = 2.6 (3.7 x 4.6) = 2.6 + 1.7 = 4.3