The alcohol content in wine refers to the proportion of ethanol; the main type of alcohol present. The theoretically achievable alcohol content of a wine can already be calculated in the grapes by the must weight. It results from the sugar (fructose and glucose) in the must, which is converted into alcohol and carbon dioxide during fermentation. In the 19th century, the chemist Joseph Gay-Lussac (1778-1850) developed a system that represents the alcohol content in degrees (°), which is still partly used in Anglo-American countries. Today, however, the indication in percent by volume is internationally common and standardised within the EU. The measurement is made at a temperature of 20 °Celsius.