There is a good deal of confusion about whether an espresso contains more or less caffeine than other typical servings of coffee. The confusion is understandable. On a per-volume basis, espresso contains approximately three times the caffeine content as regular brewed coffee (50 mg per fluid ounce of espresso versus 14-22 mg per ounce for coffee). But measured on a per-serving basis, a strict, one-fluid ounce shot of espresso (with 50 mg of caffeine) has about half the caffeine of a standard six-fluid ounce cup of American-style coffee, which varies from 80 to 130 mg.