I have the choice between 2 drinks:
1 12oz can of a pre-made cocktail which is 5% alcohol by volume
1 drink that is 3oz of vodka (45% alcohol by volume) and 12oz of seltzer (0% alcohol by volume)
Which contains more alcohol by volume? Which contains more alcohol in total? Also, if you could show your work that would be great as a resource for the future when trying to see how much is in a drink. I have a low tolerance, so I like to know how much I’m drinking when in social situations.
In: 0
Your 12oz can is 5% (0.05) x 12 oz = 0.6 oz alcohol. Which is convenient, because a “standard drink” is generally considered to be about 0.6 ounces of alcohol.
Your 3 oz of vodka is 45% (0.45) x 3 oz = 1.35 oz alcohol. Which is slightly over 2 standard drinks. This tracks, because we generally consider a single shot to be about 1.5oz of 40% (80proof) liquor – you’re having a double vodka, and the vodka is slightly stronger than normal.
And of course, your 12oz seltzer has 0 alcohol.
In general, the math to keep in mind is that a 12 ounce, 5% beer is a standard drink. 5 ounces of wine at 12% is a standard drink. And 1.5 ounces of 40% liquor is one standard drink. And those are pretty typical serving sizes – 12 ounces is a standard can, 5 ounces is a standard wine pour, and 1.5 ounces is a standard shot.
Obviously not all alcohol sticks to these levels, but most stick fairly close. Wine only varies by a few percent (unless you get into fortified or dessert wines), and liquor tends to be in the 40-50% range (again, unless you go into the non-standard stuff like Everclear), which is still pretty easy to estimate. Beer, of course, varies by quite a bit – light beers can be half the alcohol of a standard, and high-alcohol craft beers can easily be double. But you can always estimate relative to that 5% standard.
Let’s say I’m having a pint of strong, 11% craft beer. I know that 11% is more than double 5%, and I know that a pint is 16 ounces instead of the standard 12oz can. Even without actually doing the math, I can easily guess I’m having somewhere between 2.5 and 3 standard drinks – and if I do the math ([0.11 (abv)*16 oz] divided by 0.6 for my standard drink), I know it’s actually 2.93 standard drinks – fairly close to 3. By keeping an eye on things relative to my standard drink measurement (and knowing my own limits very well!), I can keep an eye on my intake and know when I should slow down or cut myself off.
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