* Volume: Whiskey is typically sold in bottles of 750 ml (25.4 ounces) or smaller.
* Proof: Whiskey's strength is measured in "proof", which is double the alcohol by volume (ABV). For example, 80 proof whiskey is 40% ABV.
* Serving size: A "shot" of whiskey is usually considered 1.5 ounces.
* Standard drink: A standard drink is defined as containing 0.6 fluid ounces of pure alcohol. This is equivalent to about 1.5 ounces of 80 proof whiskey.
Therefore, there's no single unit for whiskey, and you need to specify what you're referring to.
