How much caffeine is in one cup of coffee?
When coffee beans are roasted prior to their use, caffeine can be removed from the beans. Darker roasts of coffee generally have less caffeine than lighter roasts. Using more grounds when brewing the coffee also increases the caffeine content. Espresso, which uses a brewing process that results in a fuller extraction from the grounds, has a higher caffeine content than coffee brewed with a different process. Source: livestrong.com