How many cups are in a fifth?

Using the metric conversion tables at Science Made Simple, one 750 mL fifth of alcohol contains just shy of 25 1/3 ounces of liquid, or about 5 2/3 cups. According to Wikipedia, the modern 750 mL standard fifth was adopted in January 1979.

Wikipedia states that a fifth of alcohol used to refer to one-fifth of a gallon of spirits, that being equal to 757 mL or 25 3/5 ounces. In 1975, there was a push to adopt metric standards for weights and measures, and the standard fifth was redefined as 750 mL, equal to the volume of standard wine bottles.