How do you calculate standard drinks in a beverage if given ABV and volume?

• A. Volume (L) × ABV × 0.789 g/ml = grams of alcohol; divide by 10 g per standard drink.
• B. ABV × Volume (L) × 0.5 = grams of alcohol; divide by 5 g per standard drink.
• C. grams of alcohol = Volume (L) + ABV; divide by 10 g per standard drink.
• D. Volume (L) × ABV × 0.789 g/ml × 1000 = grams of alcohol; divide by 20 g per standard drink.

Answer: (A)

The idea is to figure out how much ethanol is in the drink, then express that amount in standard drinks. We use the density of ethanol (about 0.789 g per ml) to turn the volume of the beverage that is ethanol into grams, and we use the fact that one standard drink is defined as 10 g of ethanol.

So you take the beverage’s volume in litres, multiply by the ABV (as a percentage) to get how much of that volume is ethanol, and then multiply by 0.789 to convert that ethanol volume into grams. The result is the grams of ethanol in the drink. Finally, divide by 10 g per standard drink to convert to the number of standard drinks. This approach is consistent with how standard drinks are defined and accounts for both the amount of alcohol and its concentration.

For example, a 0.6 L drink at 4% ABV would give about 0.6 × 4 × 0.789 ≈ 1.89 standard drinks. The method works because ABV tells you how much ethanol is present by volume, the density converts that to mass, and the 10 g per standard drink converts mass into the standard-drink count.