What is the mathematical relationship between alcohol volume and proof?

The relationship between alcohol volume and proof is defined by the fact that proof is a measure that expresses alcohol content as twice the percentage of alcohol by volume (ABV). Therefore, if a beverage has an alcohol volume of 40%, its proof would be calculated as 40% x 2, resulting in a proof of 80. This indicates that the correct answer reflects the proper understanding of this conversion, demonstrating that proof is indeed twice the alcohol volume.

In this context, a beverage with 50% alcohol volume would have a proof of 100, again reinforcing that proof corresponds to twice the ABV value. Understanding this relationship is crucial for professionals in the spirits industry, as it aids in accurately labeling and communicating alcohol strength to consumers.