In a Regular Manhattan, what is the amount of bitters used?

In a Regular Manhattan, the traditional amount of bitters used is generally considered to be about 1 dash. This is because bitters are meant to enhance the cocktail's flavor without overpowering it. In most bartending practices, one dash is sufficient to balance the sweetness of the vermouth and the strength of the whiskey used in the drink.

While the choice indicating 2 to 3 drops may seem plausible, it usually translates closely to a dash, which is the standard measurement for bitters in classic cocktails. The precision in measuring bitters can vary slightly among bartenders, but the recognized amount is typically one dash which is often equal to 2-3 drops, depending on the type of bitters and the bottle's dispensing design.

Other options like 1/2 oz would be far too much, potentially overwhelming the drink, while claiming there should be no bitters at all would detract from the traditional flavor profile that defines a Manhattan. Thus, a dash is the ideal quantity that maintains the essence of the cocktail.