Expressed in degrees, Brix refers to the sugar content of grapes and wine.
Brix values are important because they can be measured objectively, informing winemakers when to harvest their grapes and communicating amounts of residual sugar left in a wine after fermentation.

A Brix value, expressed as degrees Brix (°Bx), is the number of grams of sucrose present per 100 grams of liquid. The value is measured on a scale of one to 100. During the winemaking process, winemakers use this number to calculate an approximate potential alcohol content by multiplying the Brix by 0.59. (In other words, each gram of sugar that’s fermented will turn into about a 1/2 gram of alcohol).

To determine the Brix, in the vineyards, winemakers use a device called a refractometer. To use this device, they crush single grapes from different sections of their vineyard to see what sections are ripening first and which are nearing the optimal time to harvest.

Winemakers also measure Brix in the winery during the winemaking process. After the grapes have been pressed, they analyze the final sugar content and potential alcohol level of the wine using a hydrometer - a simple mechanical tool that floats at a certain density.