How Much Is a Fifth of Liquor?

A fifth of liquor is the colloquial term for a 750-milliliter bottle. Converting 750 milliliters to ounces yields 25.4 ounces, just under one-fifth of a 128 ounce gallon, hence the colloquialism. Other traditional bottle sizes, the pint and half-gallon, have also changed with the introduction of metric measures.