When choosing a wine, one of the characteristics of interest to you might be its sweetness. But how can you really tell if a wine has sweet tendencies? The label may have some sentences on the back label to tell you just a little bit about the wine but rarely will it give an indication of its sweetness. The only quantified characteristic of a wine that is printed on a label is its alcohol by volume (ABV) expressed as a percentage.
From this, you can make some indirect assumptions about a wine's sweetness. Rough rules of thumb say if a wine's alcohol content is 10% or less it will have sweet characteristics. Wines that are even lower (especially down around 8 or 9 percent) will definitely be sweet. Wines in the 11% to 12.5% ABV range are considered 'off-dry' meaning that there is some notable residual sugar. If it’s 12.5 percent or higher, the wine will be 'dry' and have little to no perceptible sweetness.
Most wines under 10% ABV will be sweet. Typically, wines such as German Riesling and Italian Moscato fall in this category. Wines in the range of 10.5% to 12.5% include Riesling's from Austria, Australia and the U.S., Sauvignon Blanc, and Pinot Grigio (a.k.a. Pinot Gris). Then, in the 12.5% to 15.5% range you find Chardonnay, Pinot Noir, Cabernet Sauvignon, Malbec, Sangiovese, Syrah, Grenache and Zinfandel.
But, as previously pointed out, a grape that starts with low sugar levels, and ferments to the point where all the sugar is consumed by the yeast, will result in a wine with lower alcohol levels and little to no residual sugar. So, this is why alcohol levels are not a dependable way of determining a wine's sweetness.
So, while there’s definitely a loose relationship between a wine’s residual sugar and its alcohol level, it’s not a simple relationship. But you can use the percent alcohol printed on the label as a first indication. Cheers!