If you don't see yourself giving up coffee anytime soon, it's a good idea to try to estimate how much caffeine is in your cup, particularly if you buy yours at a restaurant or coffee shop. The website for Starbucks, for instance, lists nutrition information, including the amount of caffeine and calories contained in their beverages. While caffeine content can vary greatly depending on who makes it and what type of bean is used, for instance, a general rule of thumb in the United States is 100 milligrams of caffeine per 6 ounces of coffee, Griffiths says.
Related: Coffee isn't the only caffeine-containing drink that can impact health. Energy drinks, popular among the teen and college set, can negatively affect health if not consumed in moderation.