Sparkling wines labeled "Extra Sec," "Extra Seco," or "Extra Dry" have 12-20 grams of sugar per liter. These wines are in fact a bit sweeter as they tend to the upper end of their range .
Sparkling wines labeled as "Sec" or "Seco" have between 17 and 35 grams of sugar per liter and are noticeably sweet.
Sparkling wines labeled "Demi-Sec" or "Semi-Seco" have between 33 and 50 grams per liter and are fairly sweet, though the bottom end of the range still produces wines that can seem dry to the most sugar-tolerant.
Wines labeled "Doux" or "Dolce" have at least 50 grams of sugar per liter and are exactly what they claim to be: Sweet.