If 80 proof beverages are 40 percent alcohol what is in a drink that 20 by volume?

You're asking about the alcohol content in a beverage that's 20% alcohol by volume. Here's how to think about it:

* Proof is a measure of alcohol content: 80 proof means the beverage is 40% alcohol by volume.

* Direct relationship: The proof is twice the percentage of alcohol by volume.

Therefore, a beverage that is 20% alcohol by volume would be 40 proof.