With so much talk about whats in wine, I want to share with you a little research I have done. When it comes to knowing how many calories are in a glass of wine there is a bit of judgement and math involved. For typical wines, sugar is NOT a significant contributor to calories. Depending on your pour size, a glass of wine can be about 100 calories of which very little is contributed from sugar.
The primary drivers of calories in wine are alcohol and sugar. Alcohol is 7 calorie per gram and Sugar is 4 calories per gram.
The calculation
To calculate the total amount of calories in a standard bottle of wine multiply the alcohol percentage on the bottle times 0.789 (this is the density of alcohol) times 7 (which is the calories per gram) times 0.750 (the size of the bottle).
ABV * 0.789 (alcohol density) * 7 (calories per gram) * 0.750 (for a 750 ml bottle)
For sugar the calculation is the residual sugar (RS) in the wine multiplied by 4 (calories per gram) times 0.750 (the size of the bottle). Knowing RS can be difficult. People typically can sense sugar in wine at 1 gram per liter. Safe assumptions are 1 to 4 grams of sugar in a dry wine, 4 – 12 for off-dry wines, and 12 – 45 for sweet wines.
Residual Sugar * 4 (calories per gram) * 0.750 (for a 750 ml bottle)
Example
Our Cabernet had a ABV of 14.4% and RS of 0.6
.144 * 0.789 * 7 * .750 = 596 calories from alcohol per bottle
0.6 * 4 * 0.750 = 1.8 calories from sugar per bottle
Total calories per bottle 597.8. Assuming 6 glasses per bottle, calorie per glass is approximately 100 calories.