The amount of calories that are in a glass of wine depends on the type of wine and how many ounces are in the glass. A 6-ounce glass of wine with 12 percent alcohol by volume has about 126 calories, according to NHS Choices.
According to About.com, an ounce of wine, whether white or red, generally has 25 calories, with 4 ounces having 80 to 100 calories. However, many restaurants tend to pour 5-ounce servings of wine, not 4-ounce servings. Thus, a restaurant glass of wine may have 125 calories. Some drinkers may pour 6 ounces when they serve themselves.