The amount of caffeine in coffee can vary based on several factors, including the type of coffee beans, the brewing method, and the serving size. In general, however, the roast level (light, medium, or dark) does not have a significant effect on the caffeine content of the coffee.
While it is a common myth that dark roast coffee has more caffeine than light roast coffee, this is not true. In fact, the opposite is often true: light roast coffee tends to have slightly more caffeine than dark roast coffee. This is because the roasting process causes the beans to lose some of their caffeine content. As the beans are roasted for longer periods of time and at higher temperatures, they lose more moisture and mass, which leads to a lower caffeine content.
However, the difference in caffeine content between light and dark roast coffee is usually relatively small, and it is not the primary factor that determines the overall caffeine content of a cup of coffee. There are other factors, such as the type of beans and the brewing method, that have a much more significant impact on the caffeine content of the final product.