How is ABV calculated if distilled spirits are added to beer?

How would one calculate the ABV of a beer if distilled spirits were added? For instance, when making a beer recipe that called for adding bourbon as a flavoring agent. If you started with, say, 5 US gallons of beer at 5% ABV and you added 1 quart of "80 proof" spirits, how would one calculate the resulting ABV?

Topic vodka bourbon calculations alcohol-content homebrew

Category Mac


This seems like a simple solution dilution problem. Take

5 gallons = 20 quarts => 20 quarts * 5% ABV = 1 quart alcohol.

Then take your 1 quart of "80 proof" (40% ABV), and we get

1 quart * 0.4 = 0.4 quarts alcohol

So we have a total volume of 21 quarts (beer plus spirits) and a total of 1.4 quarts alcohol, thus

1.4 / 21 = 6.67% ABV

Unless I'm missing something about ABV percentage, 6.67% should be the final answer.

In general, if we have (making sure we are using consistent units)

O - the original volume, in quarts
A - the volume of spirits to add, in quarts
s - the % ABV of the original volume
p - the % ABV of the spirits

Then we can use the general formula below

((O * s) + (A * p)) / (O + A)

About

Geeks Mental is a community that publishes articles and tutorials about Web, Android, Data Science, new techniques and Linux security.