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Brix [BRIHKS] Named for A. F. W. Brix, a nineteenth-century German inventor, the Brix scale is a system used in the United States to measure the sugar content of grapes and wine. The Brix (sugar content) is determined by a hydrometer, which indicates a liquid's specific gravity (the density of a liquid in relation to that of pure water). Each degree of Brix is equivalent to 1 gram of sugar per 100 grams of grape juice. The grapes for most table wines have a Brix reading of between 20° and 25° at harvest. About 55 to 60 percent of the sugar is converted into alcohol. This estimated alcohol that a wine will produce (called potential alcohol) is estimated by multiplying the Brix reading by 0.55. Therefore, a 20° Brix will make a wine with about 11 percent alcohol.

Source: Wine Lover's Companion, by Ron Herbst and Sharon Tyler Herbst