Ethanol, the alcohol found in beverages, is a source of energy for the body. Like fats and carbohydrates, ethanol contains chemical bonds that release energy when metabolized. One gram of pure alcohol delivers approximately seven kilocalories (kcal) of energy.
Caloric Density Compared to Macronutrients
This caloric value places alcohol in a unique position when compared to the three main energy-providing nutrients, known as macronutrients. Both carbohydrates and proteins provide four kilocalories of energy per gram. Alcohol contains nearly twice the caloric density of both carbohydrates and proteins.
Alcohol’s energy density is closer to that of dietary fat, which provides nine kilocalories per gram. A gram of pure alcohol is only two calories less dense than a gram of pure fat. Understanding this numerical context is the first step in realizing how quickly the calories from alcoholic beverages can accumulate.
Applying the Calculation to Beverages
Translating the seven kilocalories per gram figure into the calorie count of a drink requires understanding how alcohol content is measured. Beverage labels list the Alcohol By Volume (ABV), which is the percentage of the liquid that is pure ethanol. To use the seven kcal/g figure, the volume of alcohol must first be converted into its mass in grams.
This conversion uses the density of ethanol, which is approximately 0.789 grams per milliliter. Since alcohol is less dense than water, a simple volume-to-volume percentage is not enough; the density factor must be included in the calculation. For example, a standard five-ounce (148 mL) glass of wine at 12% ABV contains 17.76 mL of pure ethanol. Multiplying that volume by the density of 0.789 g/mL yields approximately 14 grams of alcohol.
Multiplying those 14 grams by the 7 kcal/g factor results in 98 calories solely from the alcohol content. A typical 12-ounce can of beer at 5% ABV, calculated similarly, contains about 14 grams of alcohol and roughly 98 calories from that alcohol. The majority of calories in most alcoholic beverages come directly from the ethanol itself, though additional calories are contributed by residual sugars and carbohydrates in mixers.
How the Body Processes Alcohol Calories
The body processes these seven calories per gram of ethanol differently than calories from fats, carbohydrates, or proteins. The body views ethanol as a toxin and prioritizes its elimination through a process that primarily takes place in the liver. Alcohol requires no digestion and is rapidly absorbed into the bloodstream.
Once in the liver, specialized enzymes convert the ethanol into acetaldehyde and then into acetate, which the body can convert to energy or store as fat. This prioritization of alcohol metabolism temporarily pauses the liver’s ability to process other nutrients, including the burning of fat for energy. The body must clear the alcohol before returning to its normal metabolic activities.
Alcohol calories are often referred to as “empty calories.” While they contain energy, they provide virtually no beneficial nutrients, such as vitamins, minerals, or essential amino acids. The energy delivered by alcohol is not accompanied by the micronutrients the body needs.