Which method produces stronger coffee, espresso or ristretto?

Espresso has the highest concentration of caffeine per ounce. Each one-ounce dose contains between 60 and 65 mg, almost three times more than cold brew coffee, which comes in second with between 15 and 20 mg. Filter coffee and French press coffee contain between 12 and 16 mg. Caffeine content is only one of the factors that determine strength, and flavor also plays a role.

The ristretto gets its name from its brewing method, like espresso, and the difference between the two is subtle. It's smaller and more concentrated, with a shorter extraction time and a brown crema that gives it a slightly sweeter finish. Its flavor is the most intense you'll find, although it contains around 45 mg of caffeine, compared to 63 mg in an espresso. Therefore, if you're looking for the highest caffeine content per ounce, espresso remains the better choice.

To get the strongest 16-ounce (473 ml) cup, espresso alone isn't enough, because its servings are much smaller than those of filter coffee. In that case, a 16-ounce (473 ml) cold brew coffee, not iced, can have slightly more than 200 mg of caffeine. Among the strong hot drinks is the Red Eye, which combines 8 to 10 ounces (236 to 295 ml) of filter coffee with espresso.