Ounce for ounce, coffee has a much higher caffeine content than Mountain Dew. A 12-ounce serving of Mountain Dew has 55 milligrams of caffeine, or about 4.6 milligrams per ounce. Coffee, meanwhile, has between 80 and 175 milligrams per 8-ounce serving, which equates to between 10 and 21.9 milligrams of caffeine per ounce.
The amount of caffeine in Mountain Dew, a PepsiCo brand of soft drink, is no different depending on the different type of Mountain Dew, whether regular, diet or Code Red. Coffee, however, does vary depending on how it is made. For example, brewed coffee has between 80 and 135 milligrams of caffeine per 8-ounce serving while drip coffee has between 115 and 175 milligrams of caffeine per 8-ounce serving. Even higher is espresso, which has 100 milligrams of caffeine per 2-ounce serving.