A cup of brewed coffee has more caffeine than a shot of espresso. Since 1 ounce of espresso contains at least 2x the caffeine as an ounce of drip coffee, people often think they’re getting more caffeine with an espresso shot- but you can actually get double the caffeine of an espresso shot by drinking a regular cup of coffee, because you end up consuming a greater volume of it. Source Source 2 Source 3