are a measurement pertaining to the energy value of food. Beer is a food item and contains components providing energy value or calories to the consumer. The methods used to calculate energy value vary depending upon sources of caloric information but these are generally close enough for us to adopt the values specified by the American Society of Brewing Chemists. Specifically, beer contains protein (which provides 4 calories of energy/g), sugars and more complex carbohydrates (with 4.0 calories energy/g), and ethanol (7 calories energy/g). Organic acids can provide energy but are not considered significant in beer for caloric intake, and fats (lipids) are not contained in measurable or detectable amounts in beer so can also be ignored.

To determine the calories in beer, the alcohol by weight and the real extract (the extract remaining in beer after fermentation and containing carbohydrate, protein, and the mineral content of the beer) must be known. The mineral content can be obtained by drying down a known amount of beer and then subjecting it to high heat to burn off the organic constituents. The resulting ash is the mineral content of the beer.

In the United States the calories expressed in 100 g of beer is then determined by cal in 100 g of beer = 6.9 × alcohol % by weight + 4(RE – ash), with RE meaning the real extract (Plato) and ash expressed as percentage by weight. The value 4 represents the 4 calories energy value from protein and carbohydrate, as discussed above. If the value obtained from this calculation is multiplied by the specific gravity of the beer, then the calories per 100 ml of beer is obtained. Finally multiplying this number by 3.55 provides the caloric content of a 12 fl oz (standard US) serving size.

Also, if the value from the above equation is needed in SI units, as kJ/100 ml of beer, as now expressed in Europe, then the conversion 1 calorie = 4.184 kJ can be applied. (One calorie US = 1kcal in Europe.)

Depending upon the composition of the beer, the calorie content may vary quite widely from 15 calories/100 ml for a beer with a low alcohol content to more than 110 calories/100 ml for high-alcohol and high-residual-extract beers (one containing large amounts of nonfermentable carbohydrate) such as barley wines. Aside from the matters of technical information for the brewer and basic nutritional information for the consumer, most brewers outside large mass-market breweries consider the calorie content of their beers irrelevant. Just as calorie information is not listed on wine bottles, most craft brewers do not list it on their labels. As craft brewers move beer away from decades of commoditization, talk of calories may once again be left to brewery laboratories.