Counterintuitive as it may seem, an espresso from Starbucks actually has less caffeine than a cup of Joe. With only 75 milligrams of caffeine per cup, this brew gives you a kick compared to the 260-milligram jolt you’d get from a tall coffee. How so? It all boils down to caffeine per ounce. Ounce per ounce, espresso does have more caffeine than coffee, roughly 75 milligrams versus 22 milligrams. But because that cup of java is 12 times bigger, its caffeine really adds up.