How many shots are in a fifth of liquor?
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.” Source: cocktails.about.com