Moonriver Bar #40 - How To Measure The Strength Of A Cocktail

For anyone that can have a simple shot one night and feel nothing, and a similar shot another and fall prone to life, the universe, and everything...knows my pain.
  True, there are many factors at play during absorption.  This is why you don't drink on an empty stomach; you need carbs and content to both absorb and slow down the effects of putting alcohol in your system.  
  But as I mix more drinks - some touted as "strong", only to experience them as disappointingly as weak, with others spoken simply only to knock me sideways - I have developed a dread fascination with the math and science of Proof.

The Basic Formula

To quantify the strength of a beverage, the circulated formula is:

Alcohol content (in percentage) x liquor volume  / total drink volume
then multiply that mess by 100 

What they fail to mention here, for those of us that really need to do this right, is that that first part - Content x Volume - needs to be completed for EACH liquor in the drink, THEN add them together and divide by the drink volume.  Now, a discerning individual can probably infer that idea, but with so many mixed drinks and variations, I want to be as clear as possible how I'm getting these numbers.  

If I use, say, a Scotch and Soda as an example.
I've got 1 oz of Scotch, and 3 oz of Coca-Cola.
The Dewer's Scotch clocks in at 40% alcohol, so we factor it all into the formula:
(.4 x 1) / 4 oz = .1 x 100 = 10%.  Which makes sense - a Scotch and Soda is WEAK.

But if we take a more complicated drink, like the Singapore Sling (again, two weeks back), which was touted as "strong", but I felt nothing (I blame the juice), I wonder how that measures up.

First off, we have a lot to work with.  7.5 oz of liquid with a dash of bitters.  I'll factor out each liquor component, then add them together before I divide.

Singapore Sling Breakdown
Gin: .47 x 1.5 = .705
Cherry Heering: .5 x .5 = .25
Grand Marnier: .4 x .25 = .1
Benedictine: .4 x .25 = .1
Add that together: 1.155
Then: 1.155 / 7.5 = .154, or 15.4% Alcohol, or around 30 Proof.
So.  Hot Take.  The fabled Singapore Sling is WEAK SAUCE. 

I Made A Yummy Thing

While messing around with a B-52 shot, I decided to omit the Grand Marnier in the layering process for Amaretto...and fell head first into a new favorite.  
To mix this lovely thing, just pour equal parts into a shot glass in this order: Kahlua, Irish Cream, and Amaretto.  So, if you're mathing right, that's 1/2 oz each.

...

After six shots of this delicious mess, I'm finally feeling something, and I want to know WHY.  So we're using my "Zeppelin" concoction for our measurements today.

Let's get to know our components.
Amaretto - 21% alcohol content = 42 Proof
Irish Cream - 17% alcohol = 34 Proof
Kahlua - 20% = 40 Proof

Amaretto: .21 x .5 = 0.105
Irish Cream: .17 x .5 = 0.085
Kahlua: .2 x .5 = 0.1

0.29 / 1.5 = about .19, or 19%, or 38 Proof.  

​Okay.

So what is "strong" in comparison to most cocktails?  Because everyone's tolerance is different, so I'm sure there's a gradient of some kind...

I guess I'll use one of "strongest" drinks we know, The Long Island Iced Tea, as a gauge?
1/2 oz each of the following, and they're all the same strength:
Vodka = .4 x .5 = 0.2, Rum, Gin, Tequila, Cointreau = 1 in total
1/2 oz Lime Juice
2 oz Cola
1 / 5 = 20% or 40 Proof

Huh.  And here I was expecting more like a 50, but I guess that makes sense.  Maybe it's more like this:
Weak: 0-10%
Medium: 11-19%
Strong: 20 - 30%
Heroic: 31-40%
Stupid: 50% or more

I'll go with that rating system for now, until I learn more.  :)
See you at the Bar.
-Adamus