Champagne labels are legally required to state the wine’s level of sweetness; Called the 'dosage', or 'liqueur d'expédition'. It is measured in grams of sugar per litre (g/l) that have been added to the Champagne during the wine-making process, and together with the grapes chosen, the adding and blending of reserve wines, this contibutes to the style of Champagne.
Starting with the lowest amount of sugar added is the Brut Nature or dosage zéro style which contains less than 3 grams of sugar per litre. Extra Brut is 0-6 grams of sugar per litre. Brut is less than 12 grams of sugar per litre. Extra Dry is 12-17 grams of sugar per litre. Sec is 17-32 grams of sugar per litre. Demi-sec is 32-50 grams of sugar per litre. Doux is the sweetest style and is more than 50 grams of sugar per litre.