A 750-milliliter bottle of liquor converts to 25.4 ounces in volume, meaning that it contains approximately 12.7 shots of liquor if using a standard 2-ounce shot glass. This amount varies, as shot glasses can also be 1.5 ounces or 1.25 ounces.
When using 1.5-ounce shot glasses, the figure becomes close to 17 shots per bottle, and nearly 20 shots for 1.25-ounce glasses. The etymology behind the term "fifth" dates back to the 19th century. Liquor was sold in what appeared to be 32-ounce bottles but was actually short of this figure by a few ounces. Other terminology included "short quarts" and "commercial quarts."