Alcohol provides your body with calories, although these calories do not typically provide nutritional benefits such as protein, minerals or vitamins. Therefore, the calories consumed in alcohol are considered to be nutritionally empty.
Calories by Weight
In a pure form, alcohol has a calorie content of approximately seven calories per gram. In alcoholic beverages such as beer, wine or liquor, alcohol is diluted by the water content of these drinks. In the United States, liquor defined as 100 proof is actually only 50 percent alcohol. Therefore, 20 grams of liquor at 100 proof would contain 10 g of alcohol. This would equate to approximately 70 calories from alcohol.
Calories by Volume
There are approximately 150 calories in each of the following drink measures: 1.5 ounces of distilled liquor, 12 ounces of beer and a 5-ounce glass of wine. The calorie content of distilled liquor is higher than that of the same volume of beer or wine because the liquor has a higher alcohol concentration and content per fluid ounce.
Heavy alcohol consumption can cause damage to your liver, and may be a sign of alcoholism. If you are following a calorie-restricted diet, you may find that alcohol has a greater effect on you. It is believed that drinking significant amounts of alcohol during pregnancy may be dangerous to the developing fetus.