There are a lot of different measurement units for alcohol. People love measuring things and dividing them up into manageable sizes. We cannot get around that. It is just how people are. When it comes to alcohol, a fifth as a measurement has stuck around for a while.
But what exactly is a fifth of whiskey?
The term fifth (of some liquid) comes from when gallons were subdivided into quarts. Quarts were further subdivided into fifths, meaning four-fifths (⅘) of a quart equaled one-fifth (⅕) of a gallon.
We’ll look at the term’s origin and the history that gave rise to the fifth measurement.
Why Still Use Fifth?
It is a convenient term. That’s all. However, we don’t measure bottle sizes by fractions or relations between smaller and larger sizes.
The term fifth stuck around because it describes the bottle size. In imperial measurements, ⅘ quart or ⅕ gallon equals 25.6 fluid ounces, which is again very close to 750ml or 25.36 ounces.
Today 750ml is the commercial standard primarily used. If you’re interested, there are many other whiskey bottle sizes.
Legislation and liquor retailers versus wholesalers gave rise to the fifth measurement. Easy as that.
The capacity of British bottles used for wine and distilled liquors (like whiskey) was usually a quart. But the actual capacity of a bottle varied considerably.
Four main styles existed, each with a different capacity: between 715 and 810ml, 724 and 880ml, or even 739–835ml. The “imperial wine quart” was approximately 1,130ml (1.13 liters).
Wholesalers had a threshold of selling alcohol in full quarts (32 oz. or 946.35ml) or by the bottle. The legal threshold stipulated that retailers, barrooms, and saloons may sell by the drink. Wholesalers, or dry-goods stores, sold whiskey by gallon (four full quarts).
Retailers sold “short quarts” or “commercial quarts,” which were equal to four-fifths (⅘) of a quart (25.6 oz or 725.75ml). Five commercial quarts equal one gallon. Bottle makers referred to the bottles as “five to the gallon” and some types of bottles as “sylinder fifth” bottles.
As you can see, the “commercial quart” is very close to today’s 750ml bottle.
For many years, liquor came in various sizes, but efforts started in the 1960s to eliminate the strange fractions and standardize the bottle sizes.
Metrification or adopting the S.I. System efforts lead to the “metric fifth” of 750ml. In 1975 metric sizes for bottles were proposed, and the change was to take place in January 1979. And it did.
Conversion to the metric system was not mandatory in the US, and there was no desire in congress or among the people to adopt the system as an official system. So, the US kept using its conventional system. Alcohol, though, was metricated.
Thomas Jefferson, then secretary of state, requested artifacts from France in 1793 so the United States could adopt the metric system. France complied and sent Joseph Dombey with a standard kilogram.
Unfortunately, before he could reach the USA, the ship he was traveling on was blown off course by a storm. To make matters worse, the ship was captured by pirates, and Joseph died in captivity on Montserrat.
The metric system also never reached the United States. It should be noted that the kilogram has been redefined over the years and again as recently as 2019.
How Many Shots Is a Fifth of Whiskey?
It depends on who you ask about how much a shot is.
A standard shot in the US is one to one and a half ounces (30–45ml). So, there will be 25 full 1 ½ ounce shots or 16 one-ounce shots in a fifth (750ml) bottle. A shot in the United Kingdom can be anywhere from 25ml to 35ml. This gives you 30 and 21.4 shots in a bottle of whiskey.
Today, quarts, pints, and gallons are rarely used to measure alcohol bottles. Milliliters and liters are the updated and preferred terms. Some people prefer referring to a bottle of whiskey as a fifth.
Although it is archaic, it is not entirely wrong. A fifth of whiskey contains twenty-five 1½ oz shots; or sixteen one-ounce shots in the USA. There you have it, a fifth of whiskey is a modern 750ml bottle.