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What’s in a Drink?

The amount of alcohol in a drink is dependent on the type of alcoholic drink consumed and the size of the beverage. For example, different beers have different alcohol percentages. Also, when ordering a beer at a bar or restaurant, there are usually different size options. Just because the drink is in one glass does not mean it is equal to one serving!

The figure below shows different drinks that contain the same amount of pure alcohol. They are each considered a “standard drink”. A “standard drink” contains about 0.6 oz or 14 grams of pure (i.e., 100%) alcohol.

whats in a drink
Adapted from the National institute on Alcohol Abuse and Alcoholism (2005).

Currently, the medical profession indicates that the daily limit for a standard alcoholic drink for adult men is 2, and for adult women is 1. These limits are based on the minimum risk for cancer and heart disease due to drinking.

Below are listed several people who drank different types of alcoholic drinks. Your mission is to find out which person consumed more alcohol based on the type and quantity of each beverage. The percentage of alcohol in the drink is listed next to the ingredients using the standard terminology ABV or % Alcohol By Volume. The ABV means the percent of the volume that is alcohol (before it’s mixed with other ingredients).

Figure out how many ounces of pure alcohol each person drank and the equivalent number of “standard drinks”.

Note: The strength of alcohol in liquor bottles is usually indicated on the label with the word “proof” instead of % ABV. “Proof” is always double the ABV. So 80 proof means 40% ABV.

  • Alison had one 10 oz margarita. One 4 oz margarita contains the following two types of liquor: 2.5 oz of 40% ABV and 0.5 oz of 30% ABV. How many standard drinks did Alison have?One 4 oz margarita contains:
    2.50 oz x 0.4 = 1.00 oz alcohol
    0.50 oz x 0.3 = 0.15 oz alcohol
    Total: 1.15 oz alcoholSo the total alcohol she consumed in the 10 oz margarita = 1.15 oz x 2.50 = 2.88 oz alcohol
  • Juan had two 22 oz microbrew beers. The microbrew contains 5.7% ABV.
    22 oz x 0.057 = 1.25 oz alcoholIn two beers, the total alcohol he consumed = 1.25 oz x 2 = 2.50 oz alcohol
  • Michael had three 6 oz “Long Island Iced Teas”. One Long Island Iced Tea contains 5 different liquors: 1 oz from each of three 80 proof liquors; 1 oz from a 60 proof liquor, and 1 oz from a 42 proof liquor. (Note: these alcohols are listed in proof, NOT % ABV)One 6 oz Long Island Iced Tea contains:
    1 oz x 0.80/2 = 0.40 oz alcohol
    1 oz x 0.80/2 = 0.40 oz alcohol
    1 oz x 0.80/2 = 0.40 oz alcohol
    1 oz x 0.60/2 = 0.30 oz alcohol
    1 oz x 0.42/2 = 0.21 oz alcohol
    Total: 1.71 oz alcoholSo, the total alcohol consumed in 3 Long Island Iced Teas = 1.71 oz x 3 = 5.13 oz alcohol
  • Steve drank six 12 ounce “lite” beers. The “lite” beer contains 4.2% ABV.One beer contains: 12 oz x 0.042 = 0.504 oz alcohol
    So 6 beers contain: 0.504 oz x 6 = 3.02 oz alcohol
  • Alisha had two 6 ounce glasses of Merlot wine. A glass of Merlot contains 12.5% ABV.One glass of wine contains: 6 oz x 0.125 = 0.75 oz alcohol
    So two glasses contain: 0.75 oz x 2 = 1.50 oz alcohol

Fill in the table below. Who drank the most pure alcohol? What is the equivalence in the number of standard drinks?

Person Total amount of alcohol drunk Number of drinks person drank (from above) Equivalent # of standard drinks*
Alison 2.88 oz 1 4.8
Juan 2.50 oz 2 4.1
Michael 5.13 oz 3 8.6
Steve 3.02 oz 6 5.0
Alisha 1.50 oz 2 2.5

* Remember, a standard drink is about 0.6 oz of alcohol

A More Advanced Exercise!

What are their blood alcohol concentrations (BAC) an hour after drinking?

First you need to know the BAC right after drinking. Once you’ve calculated the initial BAC, you’ll calculate the BAC an hour later.

It’s possible to estimate the initial blood alcohol concentration (BACs) for each person based on the amount of alcohol they consumed. First, consider what the BAC would be theoretically if all of it got into the bloodstream at once. This is the maximum BAC that could be reached, right after drinking.

To calculate the BAC, you must know 3 things:

  • The amount of alcohol in the blood (in this case initially it would be the amount ingested—see your table above)
  • An estimate of the individual’s water volume (explained below)
  • The specific gravity (density) of alcohol (explained below)

Generate an equation to get the concentration of alcohol in the blood. In other words, you want to know how much alcohol (in grams) is in the person’s blood (or water spaces) (expressed in liters). By convention the units for the BAC are expressed either as a % (or grams/100 mL) or in mg/dL (a deciliter is 1/10th of a liter, or 100 milliliters). After calculating your BAC in grams per liter, you can change your units to % or mg/dL.


% BAC =

Step 1 (numerator):

You want to express the amount of alcohol ingested in grams. So you must convert oz to ml (1 oz = 29.6 ml) and then ml to g. This is easy for water – water has a density of 1, which means that 1 ml weighs 1 g. But alcohol is less dense than water—1 ml only weighs 0.79 g. It’s density or “specific gravity” is 0.79 (i.e., 79% of water). Specific gravity is a relative term compared to water at 25°C. So, you must adjust your ethanol mass by 0.79 to get the true mass of ethanol ingested.

Write the equation to convert oz alcohol ingested to g, adjusted by the specific gravity:

Example: Alison: 2.88 oz x 29.57g/1oz x 0.79 = 67.3 g

Record your data in the table below.

Alison: 2.88 oz x 29.6g/1oz x 0.79 = 67.2 g
Juan: 2.50 oz x 29.6g/1oz x 0.79 = 58.3 g
Michael: 5.13 oz x 29.6g/1oz x 0.79 = 119.7 g
Steve: 3.02 oz x 29.6g/1oz x 0.79 = 70.5 g
Alisha: 1.50 oz x 29.6g/1oz x 0.79 = 35.0 g

Step 2 (denominator):

Now determine each person’s water content or “total body water”. Alcohol is soluble in water, so it distributes into all water spaces in the body, including the blood. The concentration of alcohol in the blood equilibrates with all water spaces in the body, so that is why we can use the total body water as the denominator.

The total body water for the average male and female are found in tables in the literature. An average male weighs 70 kg and has approximately 58% of his body mass as water; an average female weighs 62 kg and has approximately 49% of her body mass as water. Assume our subjects have average weights and that 1 liter weighs 1 kg.

Total body water (TBW) for males = ____________

TBW = 70 kg or 70 L x .58 = 40.6 Liters

Total body water (TBW) for females = ____________

TBW = 62 kg or 62 L x .49 = 30.4 Liters

Now you have all the necessary information to fill in the initial BAC column in the table below. Remember to convert from g/L to g/100 mL to get the correct percentage.

Alison: 67.2 g / 30.4 L = 2.2 g/L or 0.22%
Juan: 58.3 g / 40.6 L = 1.4 g/L or 0.14%
Michael: 119.7 g / 40.6 L = 2.9 g/L or 0.29%
Steve: 70.5 g / 40.6 L = 1.7 g/L or 0.17%
Alisha: 35.0 g / 30.4 L = 1.2 g/L or 0.12%

Person Total amount of alcohol drunk Amount of ethanol ingested(in grams) Initial BAC (%) BAC after 1 hr(%)
Alison 2.88 oz 67.2 g 0.22% 0.210%
Juan 2.50 oz 58.3 g 0.14% 0.128%
Michael 5.13 oz 119.7 g 0.29% 0.278%
Steve 3.02 oz 70.5 g 0.17% 0.158%
Alisha 1.50 oz 35.0 g 0.12% 0.110%

In your table above the initial BAC indicates the theoretical BAC that would be achieved right after drinking, when all the alcohol is in the blood and has not yet been metabolized to any extent. You need to know this initial BAC if you are going to estimate what the BAC would be an hour after drinking.

Determine each person’s BAC 1 hour after drinking.

Over time, the person will metabolize any alcohol that’s in the body (and blood). You can assume that a male metabolizes alcohol at the rate of 0.012% per hour, while a female metabolizes alcohol at the rate of 0.010% per hour, resulting in a decrease in their BACs over time. These metabolic rates can vary due to many factors, but the literature shows typical rates for the average male and female.

Are you interested in why males usually metabolize alcohol more quickly than females?

Learn more about gender differences in alcohol metabolism

Write an equation to determine the BAC one hour after drinking.

Initial BAC (%) – [metabolism rate (%/hr) × time (hr)] = Final BAC (%) (unknown)
What is the BAC after 1 hour for each person? Fill in the table above.

Alison 0.22% – [0.010 %/hr × 1 hr] = 0.210%
Juan 0.14% – [0.012 %/hr × 1 hr] = 0.128%
Michael 0.29% – [0.012 %/hr × 1 hr] = 0.278%
Steve 0.17% – [0.012 %/hr × 1 hr] = 0.158%
Alisha 0.12% – [0.010 %/hr × 1 hr] = 0.110%