How much Vermouth should you use in a Martini? There has been much debate regarding what proportion of vermouth you should use in a Martini. Some people say 4 parts spirit to 1 part vermouth, others 10 parts spirit to 1 part vermouth, sometimes even less than that! It’s rumoured that Winston Churchill’s Martinis were make with just a quick glance at the Vermouth bottle in the corner of the room. However, don’t let this sway you from what you like, and if you’re not sure what you like try out some of the suggestions below for how to make the perfect Martini and find out for yourself.