On alcohol bottles, why do we put the percent of alcohol AND the proof percent on? Proof is always twice the other percent, so why label both?

Question

On alcohol bottles, why do we put the percent of alcohol AND the proof percent on? Proof is always twice the other percent, so why label both?

In: Chemistry

Answer 1

You will get a lot of people proud they read last week on TIL how proof meant sailors mixing spirits with gunpowder as proof of potency.

The answer is there no good reason. For some liquors the higher proof number looks better since it’s three digits. But mostly it’s just custom in America. Like how we print liters on gallons of milk or quarts on 2 liter sodas.