To figure out how much potassium you are eating, check the label to find out how much potassium is in 1 serving. If you are having more than 1 serving, multiply the amount of potassium by the number of servings you plan to eat. For instance, this whole can of soup has 2 servings. If you are going to eat the whole can, you should multiply 450 by 2. That means you will be having 900 milligrams (mg) of potassium.