Frequently Asked Questions 1. How much caffeine is in Diet Coke? Diet Coke contains approximately 46 milligrams of caffeine per 12 fluid ounces. It is considered a low-caffeine beverage compared to other caffeinated drinks like coffee or energy drinks. Learn more about caffeine content in Diet Coke 2. Does Diet Coke have more caffeine than regular Coke? No, regular Coke actually contains slightly more caffeine than Diet Coke. A 12 fluid ounce can of regular Coca-Cola contains around 34 milligrams of caffeine, while Diet Coke has about 46 milligrams. Find out more about caffeine in regular Coke compared to Diet…