Question: 1 part is how much?
Answer: One part is an inexact measurement. It can mean, for example, 1 ounce, 1 tablespoon or 1 cup. The key is keeping all “parts” equal. So if your drink calls for one part alcohol and three parts juice and you're making a drink for yourself, you'd want a mixture of 1 ounce of liquor and 3 ounces of the juice.