Why a Manhattan is two parts whiskey to one of vermouth, with a ratio and stir-time builder

The Manhattan is whiskey, sweet vermouth and bitters, stirred and served up. This page gives the IBA spec and the common bar version in ml and oz, then lets you move the whiskey-to-vermouth ratio and the stir time to see how strength and meltwater change in the glass.

It explains why the drink is stirred rather than shaken, why rye is traditional, how to keep vermouth fresh, what the history really says, and how to make lower-strength and alcohol-free versions. Please drink responsibly.