Nerd Alert! How the Efficiency Ratio is Calculated
The Efficiency Ratio looks at two inputs: calories and alcohol by volume. It calculates the percentage of calories in a given beer (or other alcoholic beverage) derived from alcohol. In theory, the calories that don't come from alcohol will make you gain weight and won't give you the potential desired effects from drinking said alcoholic beverage. To calculate the Efficiency Ratio, we need to know the number of calories from alcohol (specifically ethanol). Here are the steps:
- Multiply the Alcohol by Volume (ABV) by 12 to get the volume of alcohol per 12 ounces
- Multiply by 29.5735 to get the millileters of ethanol per 12oz serving
- Multiply by ethanol's density .789g/mL to get mass in grams
- Multiply the number of grams by 6.93 (ethanol's calorie per gram)
- Now we have the calories resulting from alcohol in a 12 oz. serving. Divide that number by the total calories per 12oz for the Efficiency Ratio.
For Example: Miller Lite. Calories: 96 (per 12 oz). ABV: 4.20%
- Ethanol per 12 oz: 12 * .042 = .504 fluid oz
- Ethanol in mL: .504 * 29.5735 = 14.905 mL
- Ethanol in grams: 14.905 * .789 = 11.76 grams
- Calories from Ethanol: 11.76 * 6.93 = 81.5
- Efficiency Ratio: 81.5 / 96 = 84.9%
What Regressions Tell Us
There does appear to be some relationship between Efficiency and ABV. Lower ABV beers tend to have better efficiency, but the relationship is weak as suggested by the low r-squared.
There is a better relationship between calories and efficiency, which is sort of intuitive, since empty calories are inefficient. But this relationship isn't rock-solid. If you want to be efficient, take a look at the rankings.